Fix user_functions argument bug in CCodePrinter
Add test to ccode user_functions argument
enable limits for certain sums of rational functions
resolve problem of simplify_logic with Implies
Added tests
Changed Implies and Equivalent to support numbers
Rectified errors in tests
add util.py to matrices: dok<->csr conversion
add sparsetools
Merge pull request #2 from smichr/mutil

add sparsetools
Merge pull request #2169 from SaurabhJha/matrix

A method to convert DOK representation to CSR representation and other small complementary changes
Matrix: a special technique for finding the determinant of 3x3 matrix
Merge pull request #2086 from cdsousa/master

Fix user_functions argument bug in CCodePrinter
Merge pull request #2180 from seshagiriprabhu/matrix

Matrix: a special technique for finding the determinant of 3x3 matrix
Merge pull request #2175 from srjoglekar246/simplifybug

Implies and Equivalent now map numbers to (True, False)
Merge pull request #2151 from zanzibar7/limit_bug

enable limits for certain sums of rational functions