Colors Fix, Perf Improvement, Thread Safety

-Fixes issues with colors not parsing correctly. Saving an SvgDocument
resulted in RGB color values being converted to well known color names.

-Compile regex statements to improve performance.

-Make rendering a document threadsafe.
Merge pull request #2 from articulate/ColorFix

Colors Fix, Perf Improvement, Thread Safety
Merge pull request #87 from articulate/master

Colors Fix, Perf Improvement, Thread Safety