Relaxed input key type constraints for jobs following an InputStage.

This allows a mapper that doesn't care about the input key type
to work with both TextFileSource and CombineTextFileSource inputs.
Added an AnyKeyTextInputMapper. This is like the
TextInputMapper, but has a key type of Any,
since it doesn't care about the key type.

Also changed the example Word Count MR job. It can now
optionally combine multiple input files into a single
split with -Dcombine.input.files=true, and uses the
AnyKeyTextInputMapper to accomplish this.
Bunch of random code/style cleanup
Version bump to 0.2.2 before release