Compiler Feature: node_modules should be a default include path for circuit files

[deluca-mike]

I've noticed other package that install and use circomlib by including in directly in their node_modules directory, which results in no such file or directory errors when those packages are then installed and used by others.

Example: '/Users/some_user/Projects/maci/contracts/node_modules/maci-circuits/node_modules/circomlib/circuits/mux1.circom'

If one could include "circomlib/circuits/mux1.circom"; instead of include "../node_modules/circomlib/circuits/mux1.circom"; it would be better for everyone.