Added full PLY calculator example

Run with ```python calc.py```
End input loop with CTRL-D
Added PLY example (calculator) that uses classes
Cleaned up PLY examples; added .gitignore
Moved old C lex/yacc examples to own folder
Changed path to ply for ply examples
Preliminary svel lexer

Only recognizes reserved words and IDs/numbers
Can tokenize one line at at time with ```python svelLex.py``` or "test" sample program with ```python testSvelLex.py```
Merge pull request #6 from kaitlinhuben/khuben/testing

Added more full PLY examples