Small masking bug fix

This corrects a breaking bug that was present in version 0.2.1, where masks generated by RateMap objects to remove chip edges were just integer values. This caused anything to do with generating brightness profiles to just not run.

The second XGA Release

XGA v0.2.0 has significantly greater capabilities than v0.1.0, including the ability to generate and analyse annular spectra, measure temperature profiles, and masses.