Merge branch 'release/0.3.0' into develop
Allow ints in there.
Merge pull request #26 from fedora-infra/feature/allow-ints

Allow ints in there.
Typofix.
Add some explanation to the top of the README.
Add failing tests for using formatting in the criteria operation.
Fix tests by allowing formatting in criteria operations.
Reorganize things and add doc strings to clarify whats going on here.
Merge pull request #27 from fedora-infra/feature/formattable-operations

Feature/formattable operations
Add a negation operator.
Add a pkgdb criteria checker.
PEP8.
Consolidate pkgdb api urls.
Merge pull request #29 from fedora-infra/feature/pkgdb

Feature/pkgdb
Replace internally-used sets with frozensets.  Fixes #25.
Merge pull request #30 from fedora-infra/feature/frozensets

Replace internally-used sets with frozensets.  Fixes #25.
Store a link back to the triggering event.
Merge pull request #31 from fedora-infra/feature/store-a-link

Store a link back to the triggering event.
0.4.0
Merge branch 'release/0.4.0'