Fixed non-working --patch option

InstallCommand accepts multiple values for the --patch option, but
fails at storing them in the $patchPaths array because $patch is a
SplFileInfo object.

Furthermore, ConfigureTask only supports a single patch, whereas the
patches are stored as array.
Merge pull request #283 from webmozart/fix-patching

Fixed non-working --patch option cc @webmozart