chore(typing): enforce --noImplicitAny for tools directory.

Exposed a couple of bugs.

Closes #6645

tools/broccoli/js-replace/index.ts

@@ -2,7 +2,7 @@ var fs = require('fs');
 var path = require('path');
 
 module.exports = readJs;
-function readJs(file) {
+function readJs(file: string) {
   var content =
       fs.readFileSync(path.join('tools/broccoli/js-replace', file + '.js'), {encoding: 'utf-8'});
   // TODO(broccoli): we don't really need this, it's here to make the output match the