Optimized Simfile constructor

* Values are constructed by cStringIO instead of string append operations
* Values are not added to parameters until they are finished
* The most common branch in the inner loop is now at the front

This yields a speed increase of about 30% for simfile_test.py.
Fixed Simfile.pop() bug
Tests for Simfile.pop()
v0.7.1
Cleaned up various str / repr methods
Added Notes.(get|pop)_row_string methods
Made Notes and Simfile iterable
Documentation: basic usage + examples
Expose decimal_*_192nd functions
v0.7.2
Merge branch 'dev'