Prompt - check if vcs folder exist (.git, .svn, .hg) before getting vcs repo status

[huygn]

This improves responsiveness of this "Prompt" since it prevents unnecessary repo checks ie. hg summary is verys slow (1s) regardless so it will slow down the shell. https://github.com/gnhuy91/dotfiles/commit/d5b237f930e00d1eccfd3c1b128027edcec90871

[cowboy]

But what if you're in a subdirectory of your repo?

[huygn]

Ah, I missed that, thanks for pointing it out.