Fix tests

This is a very subtle bug between FakeFS and minitest: If the must_equal
comparison fails, it opens a temp file and within FakeFS block, tempfile
opening will fail. So the fix would be to fix the test, and apparently,
with new FakeFS, a leading "/" is required
Merge pull request #149 from codegram/fix/build

Fix tests
Merge branch 'master' into rubinius
Upgrade Capybara