updated sympy sublodule
Added the condition of not sorting when keys of dict are instances of Symbol Fixes #37
now sorting the dictionary only once
Merge pull request #39 from sahilshekhawat/fix_satisfiable

Fix satisfiable (fixes #37)
Bump version to 21
Merge branch 'master' of https://github.com/sahilshekhawat/sympy_gamma
added random example to button
made 'random example' button clickable in Firefox.