Fix #759: Add java.util.Date
Merge pull request #760 from mseddon/java-util-date

Add java.util.Date
Change relSourceMap and absSourceMap into a single mapSourceURI option

Also create proper source maps for overridden sources (fixes #758)
Merge pull request #765 from gzm0/improve-source-maps

Change relSourceMap and absSourceMap into a single mapSourceURI option