Add build steps

This commit adds two new commands, `npm run generate` and `npm run build`. The
former runs the commands for auto-generating Flow, JSDoc, and TypeScript type
declarations. The latter runs the auto-generation commands, typechecks the
source according to the auto-generated type declarations, and finally generates
JSDoc documentation.

.travis.yml

@@ -1,3 +1,4 @@
 language: node_js
 node_js:
-  - "0.10"
+  - 6
+script: npm run build

package.json

@@ -12,10 +12,14 @@
     "jsdoc": "^3.4.3",
     "jsondiffpatch": "0.1.43",
     "mocha": "3.0.2",
+    "rimraf": "^2.5.4",
     "typescript": "^2.1.4"
   },
   "scripts": {
+    "build": "npm run clean && npm run generate && npm run typecheck && npm test && npm run docs",
+    "clean": "rimraf decls index.d.ts lib/types.js",
     "docs": "jsdoc -p -r lib -t ./node_modules/docdash -R README.md",
+    "generate": "npm run generate-flow && npm run generate-jsdoc && npm run generate-typescript",
     "generate-flow": "node scripts/flow.js webidl2.idl decls",
     "generate-jsdoc": "node scripts/jsdoc.js webidl2.idl >lib/types.js",
     "generate-typescript": "node scripts/typescript.js webidl2.idl >index.d.ts",