Expose Data.Label.Derive and its functionality.
Renamed derive1' to gDerive
Updated changelog and bumped version.
Make comment agree with the code.
Added travis config.
Unbreak fclabels for GHC 7.6.3

Before this commit it'd fail with:

src/Data/Label/Derive.hs:9:4:
     error: invalid preprocessing directive
      #-}
       ^
1 error generated.

(sebas: rebased similar fix into this patch)
Bump and updated CHANGELOG.