shebang detection fails if it starts with `#!/usr/bin/env`

[cb1kenobi]

When spawning mocha directly from node_modules/.bin/mocha, spawn-wrap will correctly detect it as a file containing a shebang. The shebang is #!/usr/bin/env node. The problem is spawn-wrap only checks the first segment to see if it's node.

/usr/bin/env is sort of a special case where we want to skip the first segment and test the second segment instead. Not sure of a good way of doing this without hardcoding it.