Correct the file sizes show in FAQ

The larger file sizes were due to a regression in Crosswalk,
which has now been fixed.
Update samples page to point at github
Merge pull request #79 from townxelliot/edits

Edits to samples page and fix for size error in FAQ
[Samples] Open github links in new window
[Samples] Use correct name for downloaded archive
[Getting started] Add note about XDK
Add Twitter buttons to footer
Ignore invalid certificates for wiki git repo
Update 'Contributing code' section

Fixes https://crosswalk-project.org/jira/browse/XWALK-1259
Merge pull request #80 from townxelliot/edits-20140324

Edits 2014-03-24
Add note that version 2.5.2 of gollum should be used
Merge pull request #81 from townxelliot/edits-20140324.1

Add note that version 2.5.2 of gollum should be used