Implements direnv watch file functionality

[mawwwrk]

fixes issue described in #202.

additional change: added additional folder in check for deps files, {,direnv/}, line 30.

[romkatv]

Thanks!

I merged it and made a few changes. I still need to incorporate json parsing (the one you have in the PR can fail produce incorrect results on well-formed json). My work-in-progress changes are here: https://github.com/romkatv/zsh4humans/tree/direnv. With luck I'll get back to it later this week.

[tecosaur]

I'm curious, has this just been overlooked/forgotten about?

[romkatv]

Something like that.