Added ComplexNumbers.hs

A basic set of complex number operations
Modified Arithmetic.hs

Added a few things
1) Made lists an instance of Num that behave like polynomials
2) Added a function that returns the n'th row of Pascal's triangle
3) Added the cis (cos(x) + isin(x)) function
4) Added a function that gets all the complex n'th roots of a number
Updated BinSearchTrees.hs

Fixed formatting that was bugging me
Updated Symbols.hs

Started work on a more diverse functionality for the thing, though
right now the more interesting parts are still commented out because
they don't quite work