Revert moving the completion scripts to bin.

rbenv adds a shim to all Ruby executables which breaks the completion
scripts.

Revert "Add the slow completion scripts back to bin."

This reverts commit f94c56446c2a4fa7423c0e208055a504bd1dbae7.
Fix an error in the bash complete function call.
Revert version bump.

Revert "Bump to 0.6.4.1."

This reverts commit 5afffbba3aa01fcb2ee3dfbe6d1c1a9a9ee6afbc.