(Temporary) fix for metabox styling for users using the MP6 plugin
Even though it's common to use a PLUGINNAME_URL constant for creating file paths, the use of this breaks the plugins_url filter.

This pull request replaces all uses of the WPSEO_URL constant with the correct usage of plugins_url()
Removed WPSEO_URL definition
Making this change isolated and updated readme
Remove superfluous spaces from stopwords array
Removed unused WPSEO_FRONT_URL constant
Changed all requires and includes to require_once() and removed slashes at the beginning of the path where needed (both WPSEO_PATH and ABSPATH have a trailing slash)
One more...
Last argument for load_plugin_textdomain() should have trailing slash
Merge pull request #311 from jrfnl/master

* (Temporary) fix for metabox styling for users using the MP6 plugin
* Minor fix in localization loading
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Fix-breaking-of-plugins-url-filter-hook

Conflicts:
	readme.txt
Redo MP6 fix as auto-merge had undone it
Merge pull request #312 from jrfnl/Fix-breaking-of-plugins-url-filter-hook

Fix breaking of plugins url filter hook
Oh dear, there was still one missing WPSEO_PATH...
Merge pull request #319 from jrfnl/Best-practices-require

Consistancy in file inclusion
Merge branch 'master' of git://github.com/jdevalk/wordpress-seo into Admin-page-header-improve

Conflicts:
	admin/class-admin.php
	admin/class-config.php
	admin/pages/metas.php
	readme.txt
Implemented an even better way for form charset support