Add Vyper support

[samajammin]

Doesn't look like there's support for compiling Vyper contracts?

I just tried adding my project to Truffle Teams & hit this error:

Compiling your contracts...
===========================
Error executing vyper:
/bin/sh: 1: vyper: not found

Truffle v5.0.10 (core: 5.0.10)
Node v11.13.0

Full logs here.

In order to develop locally, I create a virtual Python environment. Perhaps Truffle Teams could do something similar?

Thanks!