Add an actually-useful error message when to hooks
Fixes #200 by not requiring grunt so naively

* Introduces a grunt resolver to find the best grunt (first looking for
a local lineman, then from global lineman)
* Convert usage of grunt.util._ to require("lodash") // note that the
newer versions of lodash somehow break our complex plugin _.extend 
scheme, so we're sticking to grunt's ~0.9.1 specifier
* Pulls down underscore.string and mixes it into lodash at both of our
entry points (require lineman and the cli)
* Increases e2e tests' wait time in hopes of appeasing travis for now