Update for collection reform.

Fixes #37.
0.6.7
Show the full Docopt string for `--help`.
0.6.8
Remove old build directory.
Fix build break due to collections API cleanup
Implement libstd's `Error` trait for interop
Merge pull request #40 from alexcrichton/stderr

Implement libstd's `Error` trait for interop
Merge pull request #38 from bkoropoff/collections-fallout

Fix build break due to collections API cleanup
Implement FromError.
Match on *self instead of self when possible.
Update to rust master
Merge pull request #42 from alexcrichton/update

Update to rust master