Revert "Merge pull request #949 from asottile/npm_install_git"

This reverts commit a4c1a701bc, reversing
changes made to 889124b5ca.

pre_commit/languages/node.py

@@ -62,11 +62,10 @@ def install_environment(prefix, version, additional_dependencies):
             cmd.extend(['-n', version])
         cmd_output(*cmd)
 
-        dep = 'git+file:///{}'.format(prefix.prefix_dir)
         with in_env(prefix, version):
             helpers.run_setup_cmd(
                 prefix,
-                ('npm', 'install', '-g', dep) + additional_dependencies,
+                ('npm', 'install', '-g', '.') + additional_dependencies,
             )