Merge pull request #174 from jrfnl/master

Updated .pot file
Prevent fatal error on social page
Update readme.md to reflect recent repository move and fix travis CI image.
Added `wpseo_genesis_force_adjacent_rel_home` filter to allow forcing of rel=next / rel=prev links on the homepage pagination for Genesis users, they're off by default.
Fix possible issue with replacement in canonical of  http / https, props [jrfnl](https://github.com/jrfnl)
No need to return false, nothing listens to it.
Change the API of `register_xsl` to make `$rewrite` truly optional, also make the registered rewrite for XSL match more cases so we can do with one rewrite for which we needed multiple before. Should fix issues with non-working XSL files, but the proof of that pudding is in the eating it on a gazillion different hosts.
Added `wpseo_pre_analysis_post_content` filter. This allows plugins to add content to the content that is analyzed by the page analysis functionality.
Update change log to add missing recent changes and prep for upcoming release.
* i18n heading