Fix bugs and typos in documentation
Update to findbugs 2.0.3
Rename 'Effort' to 'Priority' to reflect meaning

FindBugs defines 'Priority' as how hard it tries to find bugs. The way
it is used here is different - it determines how bugs with different
priorities are shown or hidden.

This commit fixes this discrepancy in the code and README.
Make Priority enum type safe

Scala's Enumeration class is not type safe. This commit modifies
Priority so that it is type safe.
Add effort settings
Remove unused key
Update default report path
Bump version number
Update version numbers in README
Merge pull request #5 from anishathalye/dev

Update lots of things