Issue #152
Check if offset [3] exists in capabilitites array:

* Fixes PHP Notice occurring when using a client's custom capability manager plugin
Fix headings check in content analysis
Some code style changes
Fix XML site map appearance by fixing XSL to work properly. Fixes #185.
Fix slug stopwords removal, props @amm350, fixes #182
Merge pull request #171 from mbijon/offset3-empty

PHP Notice logged when site has capabilities created without 3rd value in args array
Update read me for latest pull merge
Merge pull request #153 from MarcQueralt/master

Issue #152
Wrap do_shortcode tags in output buffering to prevent shortcodes that echo stuff instead of return from breaking things like in #190
code style cleanup.
Fix keyword in first paragraph test.
Clean up code style and add missing PHPdoc
Reverting the addition of `do_shortcode` because it clashes with too many plugins that use short codes in a wrong way… Instead added the filter `wpseo_pre_analysis_post_content` to the content for open graph as well, so it can analyze properly added content, but not the wrong stuff.
Add better regex for heading retrieval as suggested by @jrfnl
Update change log for `do_shortcode` reversal
Getting ready for 1.4.15, flushing rewrite rules on upgrade.
Drop unused variables name and url from tracking class.