Integrating PHP Code Sniffer.

Created a `WordPressCodingStandardsCheck` class that checks the theme
against the WordPress Coding Standards available here:
https://github.com/WordPress-Coding-Standards/WordPress-Coding-Standards

For `WordPressCodingStandardsCheck` to work PHP CodeSniffer must be
intalled and available in the shell as `phpcs`. The WordPress coding
standard must also be installed and available to `phpcs` as `WordPress`.
Instructions for this can be found on the GitHub page.

The `WordPressCodingStandardsCheck` was added only to the `WP.com Theme
Review` review.

The check parses the severity of the error from `phpcs` and tries to match
it with a known error level. Errors are printed out with the error text
from `phpcs` along with the file and the line that caused the error.

See: #54
Reducing error level for WordPressCodingStandardsCheck.

Changed the error reporting so that `WordPressCodingStandardsCheck` no
longer reports blockers. Now 'ERRORS' (as reported by PHP Code Sniffer)
are reported as warnings and everything else is a note.
Replacing incorrectly named check in vip-scanner-wpcom.

The 'WordPressCodingStandardsCheck' was incorrectly named in
vip-scanner-wpcom.php. Replaced with correct name.
Fixing several coding standards issues.

WordPressCodingStandardsCheck.php should probably comply to the WordPress
Coding Standards. Fixing several small standards & formatting issues. Now
scans cleanly with phpcs.
Added checking for error slugs and classes to
WordPressCodingStandardsCheck.php.

When reporting errors the `WordPressCodingStandardsCheck` now searches
through a list of known error slugs and slug classes to find an
appropriate error level for the error. If the error is not known then its
level will be a warning if the CodeSniffer level was an Error and a note
otherwise.

Specific error slugs can be added to the $check_level array. This setting
has first priority for setting the error level.

Error classes can be defined within the $check_class_level array. A class
definition of `WordPress.XSS.` would match any error slug that starts with
`WordPress.XSS.`. Classes have second priority for setting error level.

If an error slug was not known and its priority had to be computed by
searching through error classes and/or the reported level from
CodeSniffer, then its computed level will be cached for future searches.

The default error slug levels and class levels were derived using the
following error level scheme:

- `Blockers`: Most likely a severe security or performance concern.
- `Warnings`: Most likely a performance or other concern.
- `Notes`: Stylistic issues or other issues that do not effect security or
  performance.
Fixing display issue with WordPressCodingStandardsCheck.

Fixing an issue where if the offending line in an error could not be
loaded then the line number of the error would not be displayed nicely.
Added a filter to enable error slug output.

Added a setting and a filter to WordPressCodingStandardsCheck.php to
enable/disable outputting the error slug in the problem description.
Added the ability to ignore coding standards.

Added the ability in `WordPressCodingStandardsCheck` to ignore the output
from specific coding standards by their slug.

Added `WordPress.WhiteSpace.ScopeIndent.Incorrect` to the ignore list as
it was causing a large number of false positives.
Removing CSS file scanning for WordPressCodingStandardsCheck.

The WordPress Coding Standards define no checks for CSS files, so there is
no sense in scanning them.
Merge pull request #55 from Mobius5150/master

Integrate PHP Code Sniffer with VIP Scanner using the WordPress Coding Standards