Fetch tags

This pull request addresses https://github.com/matteosister/GitElephant/issues/55
I am overriding the PHP config with this command, but surely that isn't a problem for the execution of the test suite, right?  The unit tests should not expect a timezone to be set in php.ini in order to function, and yet they were failing because (as it turned out) I didn't have a default set in mine.  It seems to me that the bootstrap should set up all the necessary conditions for the tests to be able to run, regardless of the PHP config in use.  This line guarantees that won't happen.