Support: --macrofile=<file>...

This allow us to put --define... in a --macrofile,
and let it be added to %topdir/SPECS/
which specfiles can include.
Run spectool before yum-builddep step.
Throw PackagerException is image is none.
Tests for PackagerContext.
Merge pull request #13 from norrs/packager_context_tests

Packager context tests
Merge pull request #7 from norrs/macrofile

Support --macrofile...
Removing real file from config tests
Adding tox testing for py27 and py34 with coverage reports
Starting tests for rpmbuild packager classes
More tests for rpmbuild
more tests
Moving tempfile.mkdtemp mock return value to decorator
more tests
Updating tests to support macrofiles arg