adding chai as an npm devDependency (#577)

Resolves #576

package.json

@@ -36,7 +36,7 @@
 	"license": "MIT",
 	"main": "papaparse.js",
 	"devDependencies": {
-		"chai": "^4.1.2",
+		"chai": "^4.2.0",
 		"connect": "^3.3.3",
 		"eslint": "^4.19.1",
 		"grunt": "^1.0.2",

tests/tests.html

@@ -6,7 +6,7 @@
 		<link rel="stylesheet" href="../node_modules/mocha/mocha.css" />
 		<script src="../papaparse.js"></script>
 		
-		<script src="http://chaijs.com/chai.js"></script>
+		<script src="../node_modules/chai/chai.js"></script>
 
 		<script>mocha.setup('bdd')</script>
 		<script src="test-cases.js"></script>