Radically simply the map parsing logic
Allow map keys to be function calls

The majority of changes in this diff is simple moving Arguments and
Argument above Function_Call in the source order.
Merge pull request #596 from xzyfer/feat/map-parser-electic-boogaloo

Radically simply the map parser logic
Merge pull request #597 from xzyfer/feat/functions-as-map-keys

Allow map keys to be function calls
Add support for interpolated strings as map keys
Merge pull request #598 from xzyfer/feat/interop-as-map-key

Add support for interpolated strings as map keys
SourceMap: Don't entertain garbage data. (#586)
Code: Cleanup.
Adds json library by Joseph A. Adams
Implements embedding source contents in source maps
Excludes external libraries from code coverage

They provide far more code than we actually use.
And we certainly don't want to test all that code!