Correct sourceMaps option in test and verify it.

Partly fixes #1254

Review URL: https://api.github.com/repos/google/traceur-compiler/issues/1258

Closes #1258, closes #1254.
Hoist function declarations in generator functions

This is so that we do not add a function where it isn't allowed
in ES5 strict mode, due to the CPS transformer.

Fixes #1172
Add support for export default FunctionExpression

and export default ClassExpression

We parse the expression as a FunctionExpression and if it has a name
we change it into a FunctionDeclaration. Same goes for ClassExpression.

Fixes #1208