Allow some special characters in variable names

[lucasaugustomcc]

Regina's info:

Currently, variables are only considered variables if string or number for example "example3" or "ex3FigA".
However, we have to account for the fact that dashes and underscore could be part of a variable name, so things will not be passed correctly now.

[reginawang3495]

http://www.w3resource.com/python/python-variable.php
No dashes but can start with character or underscore