Convert project from Yarn to npm

.npmrc

@@ -0,0 +1 @@
+engine-strict=false

.nvmrc

@@ -0,0 +1 @@
+6.0.0

.travis.yml

@@ -2,13 +2,12 @@ language: node_js
 node_js: ["6"]
 
 install:
-  - yarn install
+  - npm install
 
 script:
-  - yarn lint
-  - yarn build
-  - yarn test:build
-  - DEBUG=true yarn test:coverage
+  - npm run lint
+  - npm run build
+  - npm run test:build
 
 before_deploy:
   - echo "//registry.npmjs.org/:_authToken=\${NPM_TOKEN}" > ~/.npmrc

jest.config.js

@@ -1,12 +1,16 @@
 module.exports = {
   "verbose": true,
-  "transform": { ".(ts|tsx)": "<rootDir>/node_modules/ts-jest/preprocessor.js" },
-  "testRegex": "(/__tests__/.*|\\.(test|spec))\\.(ts|tsx|js)$",
-  "moduleFileExtensions": [ "ts", "tsx", "js" ],
+  "rootDir": ".",
+  "preset": "ts-jest",
   "coverageDirectory": ".coverage",
   "testPathIgnorePatterns": [
     "/node_modules/",
     "/build/",
     "d.ts"
-  ]
+  ],
+  "coverageThreshold": {
+    "global": {
+      "lines": 5
+    },
+  }
 }