make TypedPipe, KeyedList and Grouped covariant in T
add TODOs for aggregator type variance
add comment re invarance of scala Set type parameter
fix type parameter of operate in Grouped.reduce
Fixes buggy fromMillisecs
actually fixes
adds some methods, improve the tests
Merge pull request #265 from asiegel34/typed-pipe-type-variance

make TypedPipe, KeyedList and Grouped covariant in T
Merge pull request #269 from johnynek/bugfix/fromMillisecs

Fixes buggy fromMillisecs
Update docs/versions for 0.8.2
Merge branch 'release/0.8.2' into develop
Fix chill version
Fix version to 0.8.2 for realz
Update to 0.8.3-SNAPSHOT
Bump version for 0.9.0 branch
merge Aaron's changes
Fix minor build break