[#105] pulls api v1
many issue/pull fixes
[#105] add commits action
[#105] restore deleted code in error
[#105] add files action
pull diff small refactoring
[#105] add merge action
remove extra pull check
#192: refactoring of controller according to Alexander's comments
[#105] many fixes by @avokhmin comments
[#105] first part pull requests api specs
[#105] fix paginate commits & add paginate to files
#200: moved observer of Issue to lib
#200: moved User and BuildList observers
#200: removed activity_feed_observer
#200: fixed: uninitialized constant
#200: rollback some changes
#200: updated specs
#200: fixed specs
#200: removed duplicates of specs