Added method fill on HList singleton object

- Added Fill definition and implicits in ops.hlist
- Added method fill to HList singleton object
- Various tests of HList.fill
Added method fill on Tuple singleton object

- *Added Tuple singleton object in shapeless namespace*
- Added Fill definition and implicits in ops.tuple
- Added method fill to Tuple singleton object
- Various tests of Tuple.fill
Merge pull request #172 from alexarchambault/fill

HList.fill / Tuple.fill