Fixing ESR redirects

As per https://github.com/mozilla/bedrock/pull/1061, all ESR builds
should be redirected to /firefox/fx/ instead of /firefox/new/. This
fixes https://github.com/mozilla/mcom-tests/pull/216
Merge pull request #217 from kyoshino/fix-redirects-esr

Fixing ESR redirects
Remove tests for image source validity
Merge pull request #218 from bobsilverberg/image_validity

Remove tests for image source validity
fixing broken links in contribute
Merge pull request #219 from retornam/linksfixes

fixing broken links in contribute
fixing broken link in privacy.py
Fixing  broken links in security.py
Merge pull request #221 from retornam/testsecurityfix

Fixing  broken links in security.py
Merge pull request #220 from retornam/ppolicyfix

fixing broken link in privacy.py
fixing esr redirects
Merge pull request #222 from retornam/fxfix

fixing esr redirects
Remove xfail
Merge pull request #223 from AndreiH/rem_xfail

Remove xfail
Updating Firefox UA to version 23
Merge pull request #224 from retornam/fx23

Updating Firefox UA to version 23
Updating gaia testing link
Merge pull request #226 from retornam/fixlink

Updating gaia testing link
PEP8 Fixes
Merge pull request #228 from retornam/pepfix

PEP8 Fixes for all files