Some progress on syntax translation
Added AST based parser
Improved printing using precedence for binary operators (but not unary
or boolean)
Removed syntax module and moved ast_parser to brian2.codegen, added
tests
Replaced excepthook which I'd removed by mistake
Merge remote-tracking branch 'origin/master' into language_rewrite
Removed unused languages and replaced sympy with ast_parser
Do not make test fail if weave is not available (weave does not support Python 3)
BitAnd and BitOr supported (interpreted as logical)
Better tests and fixed bug with logical operators
Use the new AST-based parser for sympy parsing. Closes #51
Make consistently use of sympy_to_str(expr) instead of a simple str(expr)
Rename parse_to_sympy to str_to_sympy (makes the name symmetric with sympy_to_str)
Add tests for sympy's syntax translation and handle some sympy oddities (equality checks, printing of and/or/not)
Merge pull request #59 from brian-team/syntax_translation

Syntax translation, closes #55