Exclude codesnippet/lib from JSDuck.
Added icon for "Plugin CSS Styles" guide.
Reformatted code of styles combo guide.
Added widgets styles documentation.
Styles guide reviewed.
Added guide about disallowed content.
Added info about wildcards and special object format's features.
Update README.md

Added missing step to enter the jsduck folder
Removed redundant sudo from gem installation instructions.
ACF documentation updates reviewed.
Introduced Code Snippet and Code Snippet GeSHi guides.
Fixed some typos.
Code snippet guides added to guides.json.
Improvements for code snippets guides.
Added missing image.
Minor text changes / section link corrected.
Fixed typo.
Changed codestyle of PHP sample.
Code Snippet guide revised.
Code Snippet GeSHi documentation revised.