contributing guideline updates

* updated close policy
* added line on courtesy & respect to volunteers
* request that issue information be placed in first issue post
Added delete button to snippet view
Added tooltip to snippet public/private icons
Don't show 'Filter by labels' text if there are no labels
Don't show project search form if there are no projects
Merge remote-tracking branch 'upstream/master'
fixed nav bar for empty repos (fixes #4375)
Adding detailed documentation of the markdown syntax.

This includes standard markdown as well as GitLab extended markdown as well as references to documents used.
Merge branch 'master' of git://github.com/bbodenmiller/gitlabhq into bbodenmiller-master
Tweak wording and phrasing
Merge branch 'bbodenmiller-master'

Closes #4331
Doc: set permission on config.database.yml
Fixed db/schema.rb
Merge pull request #4460 from tstone2077/feature_help_markdown

Adding detailed documentation of the markdown syntax.
Merge pull request #4442 from 1ed/projects-helper-fix

fixed nav bar for empty repos (fixes #4375)
Merge pull request #4415 from jackbot/master

Couple of UI additions
Merge remote-tracking branch 'upstream/master'
Added update and delete_attachment actions to note controller
Prevent 'toplevel constant SnippetsController referenced by Project::SnippetsController' warning
Ability to edit comments
Authorize user on note update