Change parallel.Do to support functions returning either nothing or an error
Change parallel.For to support functions returning either nothing or an error
Add comment of parallel.For
Add package comment
Fix bug: Do returns nil if no error
Check worker return type
Merge pull request #1 from wangkuiyi/support_error

Support error
Add .travis.yml
Add more Go versions for Travis to use
Add logo and TravisCI status to README.md
Add parallel.RangeMap and example/unit test
Fix bug in TestRangeMap
Merge pull request #2 from wangkuiyi/range

Add parallel.RangeMap and example/unit test