chore(lint): require semicolons

Relying on ASI (automatic semicolon insertion)
is allowed in TypeScript because JavaScript allows
it. However, when we run clang-format it doesn’t
understand that these statements are terminated
with a newline and changes the indentation, in bad
cases even breaking the code.

Fixes #817

gulpfile.js

@@ -278,6 +278,7 @@ gulp.task('lint', ['build.tools'], function() {
   // https://github.com/palantir/tslint#supported-rules
   var tslintConfig = {
     "rules": {
+      "semicolon": true,
       "requireReturnType": true
     }
   };