[WIP] Make the ExtensionAPI compatible to TYPO3 CMS 6.2
* updateList
* fetch
* listMirrors
* import
* add Unit Tests
* vfsStream is necessary for Unit Tests. But we don't add this as a dependency to the extension. Instead we use the one which is defined in cores composer file. For installation copy the composer.json from the core package to your webroot and execute `composer install`. This will install some dependencies into Packages/Libraries.
* Add Travis CI configuration file and status image
* Add Scrutinizer configuration and status images
* Update README.md

Fixes #51, #69.