Fixes clang warning (should also fix #586)
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
Fixes source map generating (#586)
Adds json library by Joseph A. Adams
Windows: Add guard for snprintf.
Also fixes the warning for unsigned char*.
Adds base 64 encoding library

http://sourceforge.net/projects/libb64
Adds `add_source` helper function
Implements source map embedding

- embed sources content inside source map
- embed source map inside sourceMappingURL
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!
Reverts back to using longhand options in travi-ci!
Fixes some minor clang warnings in sass.cpp.
Merge pull request #591 from mgreter/source-map-sources

[WIP] Implements embedding source contents in source maps
Fixes rendering of warn and debug statement
Allow \ in identifiers
Don't error when blocks terminated by ;
Merge pull request #608 from xzyfer/fix/issue_595

Don't error when blocks terminated by ;
Merge pull request #607 from xzyfer/fix/issue_502

Allow \ in identifiers