Add --source_map_include_content option

[hidekatsu-izuno]

Closure-stylesheets lacks some source map options that exists in a latest closure-compiler. For example: --source_map_include_content, --source_map_input, --source_map_location_mapping

I implements source_map_include_content option for now. I wish to be implemented other options.

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[hidekatsu-izuno]

I signed it!

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