nits and fix.

- Use defsplitter and split_word.
- fix key comparison of string_match
Merge branch 'master' of git://github.com/ydmao/Metis
Merge pull request #5 from ms705/master

Fix under-flow bug in defsplitter
fix missing output for map_only applications

prepare_worker didn't transfer the map output to reduce
phase. Thanks Malte for the test case.
oops, now pass all tests
Merge branch 'master' of git://github.com/ydmao/Metis