Pygments-mathematica

- Unicode operators like `∈` and `⊕` are now correctly highlighted.
- Unicode `π` is recognized as a builtin and other characters like `α` are recognized as symbols.

Minor updates/fixes:
- Styles for slots and patterns can now be modified independently.
- Added example for highlighting _Mathematica_ code in LaTeX documents.

- Lexer and highlighter features:
- All builtin functions in the `System`` context except those that use characters from the private unicode space (e.g. `\[FormalA]`)
- User defined symbols, including those in a context.
- Comments, including multi line and nested.
- Strings, including multi line and escaped quotes.
- Patterns, slots (including named slots `name` introduced in version 10) and slot sequences.
- Message names (e.g. the `ivar` in `General::ivar`)
- Numbers including base notation (e.g. `8 ^^ 23 == 19`) and scientific notation (e.g. `1 *^ 3 == 1000`).
- New `mathematica` style for pygments with sane default colors.
- Companion `mma.scss` Sass file to generate CSS for HTML documents.