Ignore build directory in Git

These files should not be commited.
Create JSInput template with Makefile

This is a sample template for building the default, WebGL JSInput
application.

Make targets:
- default: Concatenate all Python files and insert inline into
  course.xml template
- clean: Remove all build/ files

Files:
- Makefile: GNU make build targets
- src/lib.py: Contains module import(s), eventually helper methods will
  go here too.
- src/main.py: Contains core grader method
- src/course.xml: Course XML template; inline Python added after
  '<script type="loncapa/python">' tag; still brittle
Merge branch dev into master