POC: Updated contrib calendar

In an effort to cut down the JS file size - i've removed the heatmap calendar used for the contributing calendar on users profiles. We already have d3 on the page so why not use it instead of using a library which uses it?

![Screen_Shot_2016-04-27_at_11.08.41](/uploads/64c40f0c766f800fd0e33ac8be7f9644/Screen_Shot_2016-04-27_at_11.08.41.png)

cc. @jschatz1 

See merge request !3944

Fix grammar and wording in text on various pages.

## What does this MR do?

Fixes various grammatical and/or wording issues I found while copyediting on the plane :)

## Why was this MR needed?

Incorrect grammar and weird/confusing wording makes the product look less polished and professional.

See merge request !4237

Enable RSpec/NotToNot cop and auto-correct offenses

Ref: https://gitlab.com/gitlab-org/gitlab-ce/issues/17761

See merge request !4267

Updated snippets UI

![Screen_Shot_2016-05-18_at_14.11.54](/uploads/2544351e50f19a36c4ba9a7a92d5544b/Screen_Shot_2016-05-18_at_14.11.54.png)

Closes #14328

See merge request !4194

Project settings UI update

![Screen_Shot_2016-05-16_at_16.42.55](/uploads/2e308cbf26a002fc411c3e84b663a5d1/Screen_Shot_2016-05-16_at_16.42.55.png)![Screen_Shot_2016-05-16_at_16.43.01](/uploads/8d983c43307c65852efe002f6e9482d9/Screen_Shot_2016-05-16_at_16.43.01.png)![Screen_Shot_2016-05-16_at_16.43.16](/uploads/6124e0600cc0e5b309a60b065409d537/Screen_Shot_2016-05-16_at_16.43.16.png)![Screen_Shot_2016-05-16_at_16.43.13](/uploads/177976c2c08034e096e7ebdcad1f369f/Screen_Shot_2016-05-16_at_16.43.13.png)

See merge request !4162

Also removes the note from the development/testing.md guide