SymPy 1.6rc1 release

Release sympy 1.5.1

Releasing SymPy 1.5

Merge pull request sympy#17958 from oscarbenjamin/bump_rc

Bump version to 1.5rc1

SymPy 1.5b1 release

SymPy 1.4 release

SymPy 1.4rc2 release

SymPy 1.4rc1 release

SymPy 1.3 release

SymPy 1.3rc1 release