This removes .es6 files which are pure duplicates of a
.ts file in the same folder.
Next we need to remove .js files as well, and remove karma preprocessors for dart.
This change solves several problems:
- the broccoli pipeline is used to compile the node/cjs tree upon any change to the modules/ directory
- jasmine tests run in a new process removing the need to clean up environment after each test
- since we transpile only those test files that are actually needed for node/cjs build, we transpile less and don't need to filter out tests