chore(package): update alsatian to version 3.1.0

Closes #19

Author: greenkeeper[bot]

package.json

@@ -39,7 +39,7 @@
     "@compodoc/compodoc": "latest",
     "@types/jasmine": "^2.8.7",
     "@types/node": "^10.0.3",
-    "alsatian": "^2.2.1",
+    "alsatian": "^3.1.0",
     "chalk": "2.4.0",
     "codecov": "^3.0.2",
     "compodoc": "0.0.41",