Port commit access pages to bedrock

Bug 876810

The following pages are ported to bedrock in this PR:

https://www.mozilla.org/hacking/commit-access-policy/
https://www.mozilla.org/hacking/committer/
https://www.mozilla.org/hacking/committer/faq.html
https://www.mozilla.org/hacking/notification/

The following files are also moved/redirected:
https://www.mozilla.org/hacking/committer/committers-agreement.odt
https://www.mozilla.org/hacking/committer/committers-agreement.pdf
https://www.mozilla.org/hacking/committer/committers-agreement.txt
https://www.mozilla.org/hacking/notification/acceptance-email.txt
`<tt>` is obsolete [according to MDN](https://developer.mozilla.org/en-US/docs/Web/HTML/Element/tt), and should be replaced by `<code>`