Clean up .jshintrc

jshint does not support `trailing` as of v1.5.0.

Remove `maxlen` too, jscs provides better implementation.

Fix definition of global mocha variables - mark them as immutable.

.jshintrc

@@ -7,18 +7,16 @@
 "undef": true,
 "unused": true,
 "quotmark": "single",
-"maxlen": 80,
-"trailing": true,
 "newcap": true,
 "nonew": true,
 "sub": true,
 "unused": "vars",
 "globals": {
-  "describe": true,
+  "describe": false,
-  "it": true,
+  "it": false,
-  "before": true,
+  "before": false,
-  "beforeEach": true,
+  "beforeEach": false,
-  "after": true,
+  "after": false,
-  "afterEach": true
+  "afterEach": false
 }
 }