Add tests, getInput should be case-insensitive and trim output

package.json

@@ -9,7 +9,7 @@
   "author": "Bryan MacFarlane <bryanmac@microsoft.com>",
   "homepage": "https://github.com/actions/toolkit/tree/master/packages/core",
   "license": "MIT",
-  "main": "lib/lib.js",
+  "main": "lib/core.js",
   "directories": {
     "lib": "lib",
     "test": "__tests__"