innerText doesn't work on Firefox

Use innerHTML, which does (and also works on Chrome).

This fixes missing link text on the downloads page on Firefox.
Add link for Android ARM beta channel
Merge pull request #71 from townxelliot/dl-links-1016

Add Android ARM beta download link
Cope better if JSON requests fail for Downloads page
Time out Ajax requests after 15 seconds
[HttpClient] Only write to cache if response was good
[Github] Handle github API errors correctly
Merge pull request #72 from townxelliot/github-badness

Fix issues where bad responses from github are cached
Fix typo
Fix permissions on cache/ dir when pushing site