Autocomplete very slow.

[c10b10]

I can confirm the issue described in #38 happens to me as well. It's slow all the time. Type nvm install and then hit Tab.

[zoltan-magyar]

I get the following error when I try to tab nvm install :

❯ nvm install grep: invalid option -- P
usage: grep [-abcdDEFGHhIiJLlMmnOopqRSsUVvwXxZz] [-A num] [-B num] [-C[num]]
	[-e pattern] [-f file] [--binary-files=value] [--color=when]
	[--context[=num]] [--directories=action] [--label] [--line-buffered]
	[--null] [pattern] [file ...]