Make capture_output thread-safe

Fixes #41
Version bump to 0.7.3
Namespace ThreadLocalIO
Allow multiple arguments to Fezzik.destination

Fixes #27
Version bump to 0.7.4
Check for Rake version to be backwards compatible
Print all destinations with 'fez --destinations'
Print only task names with 'fez --task-names'
Use $stderr for non-critical output to be script-friendly
Add new commands to usage message
Bash and Zsh autocomplete functions

Fixes #11
Better zsh autocompletion
Rename task-names and destination commands due to rake conflicts

Rake's option parser looks at every item beginning with dashes and
rejects any that rake doesn't respond to. An alternative would be
to scrub ARGV before every calling rake.
Ability to specify absolute or relative paths for tasks directory

Fixes #40
Check for existence of environment files before pushing
Show success for commands that 'exit 0'.
Merge pull request #45 from veenstra/exit0

Show success for commands that 'exit 0'.
Revert "Rename task-names and destination commands due to rake conflicts"

Solved in a better way in 453b0766457d629ee797f620623ebdd58610eee0.

This reverts commit 0bf571e5ba8666817c2d2a7740305316d9c92e13.
Clear ARGV before initializing Rake

Rake directly inspects ARGV and will crash if it
doesn't recognize a flag that was passed to fez.

Fixes #43
Use OPTIONS instead of ARGV everywhere