Add source-maps magic comments
Provide the real fs-path to the parser
Differentiate between source and logical file
Add the source map generator

Based on magic comments from the elia/source-map branch on opal:
- /*file:path.js.rb*/ for files
- /*:34*/ for lines
Add a basic spec for source-maps
Add a complilation target for source-maps
Vendor source_map gem
Fix parser-breaking optional assignments
Json is under opal
source_map must be required manually in .js.erb
Whitespace
Fix source maps spec
Fix error message for missing dir/file in spec:* task
Regexp was missing `_isRegexp = true`
Fix String#index and add specs
Add #freeze #frozen? mocks, to make libs happy
Add Enumerable#sort_by

Leaving one spec failing as a remainder to fix
multi values yields (e.g. yield(1,2,3)).
Fix source_map using mutable strings
0 or 1, as usual
Update processor options with source_maps