Make subject line of contribute email for end-users localizable.

Keep the existing filterable subject lines for Mozilla contacts.
Fixes 854992
Fix Bug 962061 - Fix the footer RTL layout (language switcher: ltr direction is hard-coded)
Install RNA library and dependencies.
Fix bug 935248: Firefox Release notes powered by RNA/Nucleus.
Bug 939975 - style the release notes template
Update rna to commit 080d7997b59b4
Upgrade south to 0.8.4

Use bug_list and bug_search_url fields in template

Add jingo_markdown

Upgrade RNA (4ae910da)

Add firefox.system_requirements view using RNA

Use latest RNA as submodule instead of pip install

Adjust views, settings, templates to use latest RNA

Restore lib/l10n_utils/helpers.py and tests from rebase mistake

Move django-extensions to submodule

Cleanup old rna egg-info

Move django-rest-framework to submodule

Move requests to submodule

Move Python-Markdown to submodule

Move jingo-markdown to submodule

Move six to submodule

Test RNA views + flake8 fixes

Fix flake8

Try to fix Jenkins test breakage

Clean up templates

Cleanup template some more

Reword test docstring and add comments

Update requiremnts/prod.txt to match submodules

Use settings.LANGUAGE_CODE for default locale

Try to make Jenkins happy
Merge pull request #1606 from kyoshino/bug-962061-footer-rtl

Fix Bug 962061 - Fix the footer RTL layout (language switcher: ltr direction is hard-coded)
Merge pull request #1588 from 6a68/bug-854992-localize-contribute-email-subject-line

Bug 854992 Make subject line of contribute email for end-users localizable.
Update RNA to 98c95295
Merge pull request #1730 from jgmize/rna-release-page

Integrate RNA and use for release notes and system requirements for Bug 922255