This commit changes the colours of languages in the language graph to
the ones Linguist has defined. When there is no colour defined for a
language in Linguist, it will fall back to the old method of finding
a colour.
Build related UI fixes
## Before
![Screen_Shot_2015-12-08_at_13.15.21](/uploads/b72ed55da1f0ec953d2eb077fa4fbb18/Screen_Shot_2015-12-08_at_13.15.21.png)
## After
![Screen_Shot_2015-12-08_at_13.15.01](/uploads/144d8099e2724a51125e392dcbd43ed4/Screen_Shot_2015-12-08_at_13.15.01.png)
See merge request !2015
It is now possible to view contributor and commit statistics for
refs beyond the default branch.
Additionally, conditions in RefsController#switch have been refactored
in order that a `case` block is used now.
* remove commits stats page (will be replaced by graphs)
* remove additions/deletions from graph because of bad performance
* keep graph logic in gitlab
Signed-off-by: Dmitriy Zaporozhets <dmitriy.zaporozhets@gmail.com>