Update CONTRIBUTING.md

Removed reference to 'silent-postgres', not in Gemfile.
Update CONTRIBUTING.md

Add some helpful hints for those new to pg.
Needs styling, but can turn on and off showing email on profile page.
All green on tests.
Merge pull request #599 from knappe/patch-1

Update CONTRIBUTING.md
Update newrelic_rpm dependency to version 3.6.7.152
Update kgio dependency to version 2.8.1
Update cucumber dependency to version 1.3.7
Update multi_json dependency to version 1.8.0
Update net-ssh dependency to version 2.7.0
Update puma dependency to version 2.6.0
Update pg dependency to version 0.17.0
Update safe_yaml dependency to version 0.9.7
Update will_paginate dependency to version 3.0.5
Update shoulda-matchers dependency to version 2.4.0
Bump to 2.1.3
Merge branch 'master' of github.com:rubygems/rubygems.org
Bump to 2.1.5
Update newrelic_rpm dependency to version 3.6.7.159
remove references to humanmsg.css and humanmsg.js
since these files don't exist anymore