Fixed bug when building svg without color swap

This is a fix to the NullPointerException I ran into when calling build() on SVGBuilder without specifying a color swap through .setColorSwap() :

Caused by: java.lang.NullPointerException
 	at com.larvalabs.svgandroid.SVGParser$SVGHandler.setColorSwap(SVGParser.java:875)
 	at com.larvalabs.svgandroid.SVGBuilder.build(SVGBuilder.java:160)

Also add attach sources and attach javadoc to the maven artifact