Update contributing file with latest insights.

IMPORTANT! Data converting in migrations was wrong. Fixed

Fix project transfer error

update grape to 0.3.1 for ruby 2.0 support.

closes #2300

add grape-entity, that is split from grape 0.3.0.
remove usage of deprecated error_format, that is removed in grape 0.2.3.

Merge branch 'state-machine-stage-2' of https://github.com/Undev/gitlabhq into Undev-state-machine-stage-2

Conflicts:
	app/models/merge_request.rb

Show only ≤16 lines of codes in a discussion in a MR (issue #2860).

Since search_autocomplete_source rendered with raw all human input should be sanitized to prevent XSS

System hooks code & logic refactoring

Remove function 'check_issue_1059_shell_profile_error' from check.rake as it is not needed anymore