Added KL period functions

A new file contains functions that perform KL period calculations.  One set
of functions does this semi-analytically, the other does it purely
numerically by integrating the secular equations of motion.

I fixed a number of bugs in triplesec that appeared when the functions were
imported rather than run directly.  (There were issues with local vs. global
namespaces.)

Also added an (empty) __init__.py file to support module functionality.