Added theme support for FuelInstaller

Please note that there is no default location for themes in FuelPHP 1.x, but this path is mentioned as a possible default in the docs. Make sure to change the config. (Actually there is a default, but it is in the DOCROOT, which is not recommended)
Add support for Zikula. Closes GH-124.
Fix broken Zikula test. Ref GH-124.
Merge pull request #118 from sagikazarmark/patch-1

Added theme support for FuelInstaller
Add support for shopware. Closes GH-122.
Clean up composer.json keywords
Add fuel-theme to readme
added Yii2 to the list of natively supported frameworks
Merge pull request #125 from schmunk42/master

added Yii2 to the list of natively supported frameworks
fixed plugin-naming