Fix contribute email tests.

These tests were relying on files in "locale"
to either exist or not, and these change often.
I've added mocks that removes their dependence
on these sortof external files.

This does include an upgrade of the Mock library
to 1.0.1. You'll need to `pip install mock==1.0.1`
in order to get your local tests to pass.
sign up button is not working of student ambassadors page bug 893329
Merge pull request #1066 from pmclanahan/fix-contribute-email-test
Merge pull request #1068 from alexgibson/sign-up-button-not-working-student-ambassadors-bug-893329
Revert "Bug 893006 - change the rewrite rule for firefox/update to take locales into account if we have a translation"

This reverts commit 010175bb728f86c859971dd8e9614e599111b77a.
Undo "Revert "Bug 893006 - change the rewrite rule for firefox/update to take locales into account if we have a translation""

This reverts commit 0760ec64a7b8bf430a5aa13602c37a3501488100.
Bug 894074: /firefox should redirect to fx/new/ for old fx.

Also fix bug 869937: Similar redirect semantics for
whatsnew and firstrun pages.
Merge pull request #1070 from pmclanahan/change-firefox-update-redirects-new-894074

Bug 894074: /firefox should redirect to fx/new/ for old fx.