chore(build): remove code coverage support

as of now its impossible to run coverage with AVA. The build keeps failing

look avajs/ava#604 (comment)

Author: tusharmath

package.json

@@ -13,7 +13,7 @@
     "url": "https://github.com/tusharmath/Multi-threaded-downloader.git"
   },
   "scripts": {
-    "test": "nyc ava && nyc report --reporter=text-lcov | coveralls",
+    "test": "ava",
     "lint": "standard --verbose | snazzy",
     "semantic-release": "semantic-release pre && npm publish && semantic-release post"
   },
@@ -35,11 +35,9 @@
   "license": "MIT",
   "devDependencies": {
     "ava": "^0.13.0",
-    "coveralls": "^2.11.8",
     "cz-conventional-changelog": "^1.1.5",
     "express": "^4.13.1",
     "ghooks": "^1.0.3",
-    "nyc": "^6.0.0",
     "semantic-release": "^4.3.5",
     "sinon": "^1.17.2",
     "snazzy": "^3.0.0",