Lift Loader.parse into System.parse.
This allows Loader to be independent of compiler/transcoder and
it allows the System to control parse options w/o consulting Loader.
Merge pull request #174 from johnjbarton/lift-parse

Lift Loader.parse into System.parse.
Reimplement System.parse() using traceur.Compiler
Merge pull request #176 from johnjbarton/use-traceur-compiler

Reimplement .parse() using traceur.Compiler
better error example
parse refactoring
set baseURL to process.cwd