v0.3.3

Major changes: Fail more clearly when the Swift API is down, and gracefully skip Swift Grism images rather than error out.

What's Changed

• Raise a clear error when the Swift TOO API query fails by @robertdstein in #46
• Fix Coveralls always reporting 0% coverage by @robertdstein in #45
• Add Coveralls badge to README by @robertdstein in #44
• Skip grism images during UVOT reduction by @robertdstein in #48
• v0.3.3 by @robertdstein in #49

Full Changelog: v0.3.2...v0.3.3