mathics 0.6.0.rc1 draft
Upgrade to Sympy 0.7.3

incompatability changes:
    sympy.Ylm -> sympy.Ynm
    sympy.Expr.as_coeff_terms -> sympy.Expr.as_coeff_mul
    sympy.Symbol('x', dummy=True) -> sympy.Dummy('x')

improvements:
    sympy.solve
Exp should be a _MPMathFunction
install sympy from git in travis-ci tests
fix bug in Real.__cmp__
remove Integer.get_sort_key hack
refactor Log to give more accurate results
add test for large Integer comparison bug
add SympyFunction.prepare_mathics to fix SphericalHarmonicY
monkeypatch sympy.Expr._expand_hint bug
add basic Piecewise and fix piecewise Sum bug
Add support for #0 in pure functions (issue #5)
Fix check for out-of-range slot numbers (issue #5)
Merge pull request #159 from bnjones/master

Fix unmatched <dl> tag in IntegerDigits docstring
Merge pull request #157 from sn6uv/sympy073

Sympy 0.7.3
Merge pull request #156 from sn6uv/mathics0.6.1

Mathics 0.6
Style fix
Merge pull request #160 from bnjones/slots

Support #0 in pure functions
Fix Slot[0] not printing as #0
add test for Slot[0] formatting