Refactor main help message
parser_redeye.py: `resolve` into cmdname as well
Generate help messages from option descriptions

Closes #56.
Update command options

Redeye interface only (for now, at least)
Clarify some of the option descriptions

Also, remove the dots at the end of descriptions — they make help
messages uglier
Remove debug print
Cache help messages
Ignore `--api` option of `update`
Do not show dashes for shortopts that don't exist
Show positional argument of a command
Merge pull request #78 from Minoru/helpmessage-refactoring

Refactor help messages