re-enable chrome tests on drone.io
don't run tests on dart2js after all...
Ability to convert git object to files.

This adds a way to write a git object tree into the filesystem.
Add todo for unittest.
Minor fixes (addressed comments).
Merge pull request #216 from dart-lang/object_util

Ability to convert git object to files.
Merge branch 'master' into test-chrome
review comments
Merge pull request #213 from dart-lang/test-chrome

Test chrome
Merge branch 'master'