Make type signatures readable

[gbeaty]

Trying to add Scalar[Speed] to Scalar[Force]:

[error] /home/grant/Workspace/scunits/test/src/main/scala/DefaultTests.scala:56: type mismatch;
[error]  found   : scunits.Scalar[scunits.default.Force]
[error]     (which expands to)  scunits.Scalar[scunits.types.^[scunits.default.quants,scunits.types.*:[scunits.types.PredInt[scunits.types.PredInt[scunits.types._0]],scunits.types.*:[scunits.types._0,scunits.types.*:[scunits.types.SuccInt[scunits.types._0],scunits.types.*:[scunits.types.SuccInt[scunits.types._0],scunits.types.ENil]]]]]]
[error]  required: scunits.Scalar[scunits.default.Speed]
[error]     (which expands to)  scunits.Scalar[scunits.types.^[scunits.default.quants,scunits.types.*:[scunits.types.PredInt[scunits.types._0],scunits.types.*:[scunits.types._0,scunits.types.*:[scunits.types.SuccInt[scunits.types._0],scunits.types.ENil]]]]]
[error]   metrePerSecond(5) + newton(100)

I don't know if there's a way to do this without the use of implicits, which impact run-time performance.