Merge pull request #4 from qguv/hotfix

hotfixes: arithmetic error handling
added FAQ

added FAQ with change of base formula and bug reporting
README.md formatting improvements
README.md improvements

added lack of in-program help to known issues
removed deceptive help message
trigonometry & major binding changes

non-compatable changes; will need a major (v0) release. see changelog.md

new functions: abs, sin, cos, tan, asin, acos, atan, deg, rad, sqrt
implemented backspace!
Revert "implemented backspace!"

This reverts commit 7ad584ee2a684c28c1273dc900cbf63638b82119.
documented backspace
Revert "Revert "implemented backspace!""

This reverts commit 71cf44b970c752d9e1ad452730aa18de19938899.
improved operator.py documentation
Big Trig Release! (pull request #5)

Adds trigonometric functions, improves documentation,and implements the elusive `Backspace`.