Clean dependencies (#61)

* Remove unused dev dependencies

* Remove codecov.io as dependency and from README

Unused at the moment, and that dependency is not the modern way to use
codecov.io in a JS project.

packages/ripple-keypairs/README.md

@@ -1,4 +1,4 @@
-# ripple-keypairs [![NPM](https://img.shields.io/npm/v/ripple-keypairs.svg)](https://npmjs.org/package/ripple-keypairs) [![Build Status](https://img.shields.io/travis/ripple/ripple-keypairs/master.svg)](https://travis-ci.org/ripple/ripple-keypairs) [![codecov.io](http://codecov.io/github/ripple/ripple-keypairs/coverage.svg?branch=master)](http://codecov.io/github/ripple/ripple-keypairs?branch=master)
+# ripple-keypairs [![NPM](https://img.shields.io/npm/v/ripple-keypairs.svg)](https://npmjs.org/package/ripple-keypairs) [![Build Status](https://img.shields.io/travis/ripple/ripple-keypairs/master.svg)](https://travis-ci.org/ripple/ripple-keypairs)
 
 An implementation of ripple keypairs & wallet generation using
 [elliptic](https://github.com/indutny/elliptic) which supports rfc6979 and

packages/ripple-keypairs/package.json

@@ -20,19 +20,13 @@
   },
   "devDependencies": {
     "@types/node": "^13.1.5",
-    "assert-diff": "^1.0.1",
     "babel": "^5.8.20",
     "babel-core": "^5.8.20",
     "babel-eslint": "^6.0.0",
     "babel-loader": "^5.3.2",
-    "codecov.io": "^0.1.6",
-    "coveralls": "~2.11.4",
     "eslint": "6.8.0",
-    "eventemitter2": "^0.4.14",
     "istanbul": "~0.3.5",
-    "map-stream": "~0.1.0",
     "mocha": "~2.3.3",
-    "nock": "^2.13.0",
     "tslint": "^5.11.0",
     "tslint-eslint-rules": "^5.4.0",
     "typescript": "^3.1.3"