added raw category model
implemented choice of categories
refined model, migration and seeds
missing file
began admin UI
category views for admin
sort categories by id
added button to add categories; removed category#view button
view for new category
included functional tests for categories
First steps to integrate Git.
Foreign key for repository_id in combination with parent_id added.
Abilities adjusted
Create (untested) git lib
Removed redundant method.
Add first tests for git lib
merge conflict
Cleaned up duplicate code.
some tests fixed
imported ancestry gem, created migration and seeds