Small improvements

This changes two small things:

1. The path comparison is done ignoring the case now because otherwise paths are not considered equal when cslint is used together with Arcanist and Git and if arc lint is executed within a sub-directory of the project. See here:
https://github.com/phacility/arcanist/pull/191
for making this possible in Arcanist.

2. The created XML output file is now automatically deleted because when executed through Arcanist the created file gets overridden anyway if there are several project files in the repository because cslint is executed multiple times in that case.