Get ScreenshotCheck working with the zip scanner

Use getimagesizefromstring() instead of getimagesize() - which expects
an fs path.
Merge pull request #129 from ehg/screenshot-zip-fix

Get ScreenshotCheck working with the zip scanner
Add check for forbidden PHP functions.
Correct error slug in ForbiddenPHPFunctionsCheck.
Add check for Google Custom Search and Google Ads.
Remove unused GetOptionDeprecated check.
Removed unused MoreDeprecatedCheck.
Add WhitespaceCheck.

Checks for whitespace before the opening and closing PHP tags.
Add CommentsCheck.

Checks whether the theme contains comment pagination.
Remove unused ThemeCommentPaginationCheck.
Add PostThumbnailsCheck.

Checks for proper implementation of the feature and verifies if the
tags in style.css are set accordingly.
Update contributors list in readme.
Add ThemeNameCheck.

Check for buzzwords as well as WordPress and theme related words in the
theme name.
Improve regex for ThemeNameCheck.

There should be either a space or a start of line before a word to
avoid false positives.
Refactor ForbiddenLibraryCheck.

Refactor the handling of the forbidden libraries to be able to add
libraries faster.
Add isotope.js as forbidden library.
Add jQueryCheck.

Checks for usage of the deprecated .live() method.
Add MasonryCheck.

Checks for the deprecated ‘jquery-masonry’ script handle that was used
for Masonry V2.
Temporarily remove the WhiteSpace check.
Avoid false positives for Featured Image Headers.

If themes have declared support for post thumbnails, using the
featured-image-header tag in style.css will now avoid a false positive.