updated development docs

docs/40-develop.md

 Develop
 -------
 
+Many development tasks can be accomplished by using the command-line interface of Yii2.
+
+Run the help command from your project root to get more information about available console commands. 
+ 
+```
+./yii help
+```
+ 
+### Topics 
+
 - [Code Generation](41-code-generation.md)
 - [Testing](42-testing.md)
 - [Extension Development](44-extension-development.md)
+

docs/44-extension-development.md

 Extension Development
 =====================
 
+If you plan to reuse functionality, it is recommended to provide the code in composer packages. Luckily, Yii 2.0 Framework is equipped with a code generator for creating ready to use extension skeletons in a minute.
+
+> Note! Code generation is only available with `YII_ENV_DEV=true`.
+
 Building an extension
 ---------------------
 
-### Gii from the command line (recommended)
+### Generating skeleton with Gii
+
+To create an extension from the command line adjust the parameters in the following command and run it from your
+project root.
 
 ```
  ./yii gii/extension \
-     --vendorName=you \
-     --packageName=yii2-new-module \
-     --namespace=you\\new\\ \
+     --vendorName=mycompany \
+     --packageName=yii2-mypackage \
+     --namespace=mycompany\\mypackage\\ \
      --license=BSD-3-Clause \
-     --title="A new Yii 2.0 module" \
-     --description="Enter some useful text here..." \
+     --title="Extension for Yii 2.0 Framework" \
+     --description="Provides cool stuff" \
      --authorName="Your Name" \
-     --authorEmail=you@example.com
+     --authorEmail=you@yourdomain.com
 ```
 
-### Gii Web interface
+This will generate a folder in `runtime/tmp-extensions/yii2-mypackage` with example code for the extension.
 
-- Open `Gii > Extension Generator`
-- Enter values
-- Click preview
-- Click generate
-- Follow instructions and push repo to GitHub
-- Require via `composer`
-- Happy coding...
+### Make your extension available via composer
 
-### Share your extension
+Create a new private or public repository, eg. on [GitHub](https://github.com/new).
 
-Create a new private or public repository, eg. on [GitHub](https://github.com/new)
+Then, go to the folder with the generated code inside your project's `runtime` folder and initializie a temporary
+Git repository
 
 ```
-cd runtime/tmp-extensions/yii2-new-module
+cd runtime/tmp-extensions/yii2-mypackage
 git init
-git add -A
+git add .
+```
+
+Check if you have added the correct files with
+
+```
+git status
+```
+
+It should show three files to be committed. If everything is fine commit and push your changes to your repo.
+
+```
 git commit -m "initial commit"
-git remote add origin https://github.com/you/yii2-new-module.git
+git remote add origin https://github.com/mycompany/yii2-mypackage.git
 git push -u origin master
 ```
 
-[Submit to packagist](https://packagist.org/packages/submit) and wait a few minutes or add repository manually to `composer.json`.
+#### Private packages
+
+If you are developing packages for a private repository you can enable your package by adding it's repository URL to `composer.json`
+
+```
+"repositories": [
+{
+  "type": "git",
+  "url": "git@github.com:mycompany/yii2-mypackage.git"
+},
+```
+
+> You should use the git protocol when using private repositories in conjunction with private-public-key authentication when
+> deploying remotely or in a virtualized environment.
+
+#### Public packages
+
+To make your extension available publicly, [submit it to packagist](https://packagist.org/packages/submit).
+ 
+It should be available after a few minutes, if you are heavily developing an extension you can still add it's repository 
+manually to `composer.json`, like described above. Composer will then check the repository on every update and you'll
+get always the latest commits.
+
+### Install package
+
+Now get the code in any Yii2 application with
 
 ```
-composer require you/yii2-new-module
+composer require mycompany/yii2-mypackage:dev-master
 ```
 
+Depending on your extension and its bootstrapping configuration you may have to configure it in the application configuration.
+The classes from your package are available via auto-loading and accessible by their namespace. 
+
+### Alternative: Using the Gii Web interface
+
+You can also use the Gii web-interface and your favorite Git UI client to accomplish the tasks described above.
+
+- Open `Gii > Extension Generator`
+- Enter values
+- Click preview
+- Click generate
+- Create Git repo, commit and push to repository
+- Require via `composer`
+
 ---
 
 Use Yii Framework 2.0 Development Repo