Update mocha and istanbul npm tasks

- remove not needed relative paths to mocha and istanbul binaries
- remove test-windows task because _mocha.cmd doesn't exist
- extract mocha options to separate file
- decrease timeout for single it-block form 10 seconds to 5 second

package.json

@@ -13,8 +13,7 @@
     "start": "node loader.js",
     "lint": "eslint --cache .",
     "pretest": "npm run lint",
-    "test": "./node_modules/.bin/istanbul cover ./node_modules/.bin/_mocha -- ./tests -t 10000",
-    "test-windows": "./node_modules/.bin/_mocha.cmd ./tests -t 10000"
+    "test": "istanbul cover _mocha tests"
   },
   "dependencies": {
     "async": "~1.5.0",

tests/.mocha.opts

@@ -0,0 +1,2 @@
+--reporter dot
+--timeout 5000