Fixing phpcs problems from https://travis-ci.org/Elgg/Elgg/jobs/9528292
Fixes email headers from hook being ignored
Merge pull request #5879 from mrclay/fix_email_headers

Fixes email headers from hook being ignored
Cleans up CONTRIBUTING.md

Format is now more consistent for each section and clearly outlines our expectations in checklist format.
Fixes build by specifying karma version
Merge pull request #5892 from ewinslow/travis-karma-fix

Specifying karma version to fix build
Begins RST docs in /docs subfolder
Merge pull request #5893 from ewinslow/sphinx-docs

rST docs now live in core