Extracted 'sourcemap-to-ast' module
Add option to disable source maps for certain files
Fix inconsistency in cache handling when multiple

build configurations have different values for the 'node' option
Disable sharing of the same cache for

configurations with different values of the 'node' option
release 0.0.4
Add missing browser-builtins dependency
release 0.0.5
Merge branch 'master' of http://github.com/tarruda/powerbuild