fix(onPrepare): onPrepare with a string argument should resolve from the config directory

onPrepare can take a string, which is a filename containing a script to load adn execute
before any tests run. This fixes the string to resolve the filename relative to the
config file, instead of relative to the current working directory where protractor
is called.

Author: juliemr

lib/runner.js

@@ -214,7 +214,7 @@ var runJasmineTests = function() {
         if (typeof config.onPrepare == 'function') {
           config.onPrepare();
         } else if (typeof config.onPrepare == 'string') {
-          require(path.resolve(process.cwd(), config.onPrepare));
+          require(path.resolve(config.specFileBase, config.onPrepare));
         } else {
           throw 'config.onPrepare must be a string or function';
         }