Enable strict compilation settings in git extension

Enables strict checks in the git extensions

extensions/git/package.json

@@ -902,6 +902,7 @@
   "devDependencies": {
     "@types/mocha": "2.2.43",
     "@types/node": "7.0.43",
+    "@types/byline": "4.2.31",
     "mocha": "^3.2.0"
   }
 }