Add short flags and fix conflicting host flag

[rafaelespinoza]

This is a nice tool. But there are some minor usability annoyances with the input flags.

Addresses the host= flag short-form that conflicts with --help's short form. Both are -h and help takes precedence. Get around this by specifying an alternative short-form for host. This is similar to #22. Fix a typo in usage text. Adds some other missing short-form flags.

I was careful to look for creating conflicts and couldn't find any new ones. Going through each subcommand's usage func shows that it still works. From what I understand, if there was a conflicting flag, then beanstool <subcommand> -h would output something like:

"Unknown command `delete'. Please specify one command of: bury, kick, peek, put, stats or tail

Which doesn't seem to happen. Let me know what you think, thanks.