First cut at adding evaluation support to FSharp.Literate
Cleaned up and refactored.

Made FSI evaluation optional - if you don't pass in an FsiEvaluator,
nothing is evaluated.
Moved the evaluation to a separate phase, instead of conflating the
formatting phase.
Hidden paragraphs are evaluated too.
Set FSI options and call cd before evaluation
Remove named unions properties for F# 3.0 compat
Hopefully fix Travis test

Guessing C: does not exist on Travis build/test machine.
Merge pull request #133 from kurtschelfthout/master

Add support for fsi evaluation in literate scripts