Added support for having coding standards in the root package

[frenck]

Proposed Changes

This change adds support for having PHP_CodeSniffer standards in the root package.

Related Issues

Implements: #20 Check the root package for sniffs to install

[frenck]

Travis tests fails, enabled by @Potherca, but not configured it yet.
Therefore the failed Travis builds can be ignored for now.

[Potherca]

For completeness sake: although usually using getcwd (and consorts) is discouraged, this is the "Composer Way" of doing things.

[frenck]

Just thought of an edge case that might cause troubles with this solution:

• This plugin is installed globally
• Current working directory is a repository containing a coding standard
• Running a composer global install/update command

This might cause the installation of the local coding standard into the global scope.

Will check on this tomorrow.

[frenck]

Checked my above concerns and concluded this won't be an issue since the Composer GlobalCommand will change the working directory before actually running Composer (again).

See: https://github.com/composer/composer/blob/9e7d1a4f9ed34466a05ac1356e97a98686f7da67/src/Composer/Command/GlobalCommand.php#L77