Bug 865058 - fix newsletter ordering

* Fix sorting of newsletters on /existing page so they're sorted by
  the newsletters' `order` field
* Add a test
Bug 895317 remove /en-US/ from support.mozilla.org links
Merge pull request #1090 from retornam/bug-895317-fixfirefoxos-sumo

Bug 895317 remove /en-US/ from support.mozilla.org links
Bug 894055: Add funnelcake parameter to bedrock URLs.

Now if a page has a download button on it, and the
url includes the query param `f=[0..9999]`, then that
number will end up on download links in the form
`product=firefox-stub-f999`. The ID must be numeric
and not exceed 4 digits.
Merge pull request #1092 from pmclanahan/enable-funnelcake-qs-param-894055

Bug 894055: Add funnelcake parameter to bedrock URLs.
Bug 896232 - Make newsletter form localizable
Bug 896260 - Localize home page <title>
Merge pull request #1094 from TheoChevalier/localize-home-title

Bug 896260 - Localize home page <title>
Merge pull request #1093 from TheoChevalier/newsletter-form-localizable

Bug 896232 - Make newsletter form localizable
Merge pull request #1080 from dpoirier/bug-865058-fix-newsletter-ordering

Bug 865058 - fix newsletter ordering
Fix bug 862842 - Add Webmaker Mentor list signup to /contribute

When users sign up on https://mozilla.org/contribute and select "Education"
from the drop down list, an additional checkbox to sign up for the Webmaker
Mentor mailing list should appear.
Merge pull request #1086 from jbuck/contribute
Add RewriteCond/Rule to remove URL double slashes. Bug 845988.
Merge branch 'bug-845988-url-double-slashes' into demo3