chore: fix travis build

- bump to mocha 1.21.5 in order to remove "*" version-range on the
  "debug"-dependency
- explicit use of "dot"-reporter for mocha 1.21.5, fixes failing tests
  of console.log output
- fix tests running in the browser: assign variable "global" with
  global "this", backport from master-branch
- sync saucelab config with master branch:
  - Remove Safari 6 and 7 that are not supported by saucelabs anymore
    and cause timeouts when running the saucelabs tests.
  - Add Safari 8 and Safari 9
  - Note: The tests fail with Safari 9 and 10 because in these versions
    the "column"-property of "Error" is read-only
    (see https://github.com/jquery/esprima/issues/1290)
  - Firefox needs explicit platform specifier

spec/env/common.js

@@ -1,3 +1,21 @@
+var global = (function() { return this; }());
+
+var AssertError;
+if (Error.captureStackTrace) {
+  AssertError = function AssertError(message, caller) {
+    Error.prototype.constructor.call(this, message);
+    this.message = message;
+
+    if (Error.captureStackTrace) {
+      Error.captureStackTrace(this, caller || AssertError);
+    }
+  };
+
+  AssertError.prototype = new Error();
+} else {
+  AssertError = Error;
+}
+
 global.shouldCompileTo = function(string, hashOrArray, expected, message) {
   shouldCompileToWithPartials(string, hashOrArray, false, expected, message);
 };

spec/env/runner.js

@@ -27,6 +27,7 @@ run('./node', function() {
 function run(env, callback) {
   var mocha = new Mocha();
   mocha.ui('bdd');
+  mocha.reporter('dot');
   mocha.files = files.slice();
   if (grep) {
     mocha.grep(grep);