minor updates

• Add a version.py so that run.py --version works.
• Add a requirements file
• Add new string functions
  • curl -X GET http://127.0.0.1:8888 -d '{"ref": "string.fib", "kwargs": {"string": "word"}}'
  • curl -X GET http://127.0.0.1:8888 -d '{"ref": "string.triple", "kwargs": {"string": "word"}}'