Fix to support PHP prototypes (fixes #276)
Basic Wolfram Mathematica support
Switch to using class prefixes

This is mainly to address #266 with the language specific prefixes. We will
use a less specific prefix, that being hljs-, to avoid markup collision.
However, as a result, there will be some incompatibility; to remove the
prefix, using `hljs.compatibilityMode = true` flag configuration will stop
this new behavior.
Move all styles over to the prefixed version
Add prefix in the test page
Add compatibilityMode flag explanation in README
Update documentation for compatibilityMode flag
Remove the pre in styles

However, I did keep `pre code` for now.
Change flag from compatibleMode to classPrefix
Change local variable classprefix to buildSpan

A function used to build a span with or without a closing tag.
Translate use of classprefix over to buildSpan
Move compatible documentation over to CHANGES
Change docs of compatibilityMode to classPrefix
Add a hljs class to tag that is being highlighted

This to address issues with custom initialization not having the styling
included in the themes, mentioned in #147.
Change pre code over to the hljs class
Fix display of test results
Fix broken urls from mismatched macros
Fix another macro messup
Fix header name in Google Code style
Include //= in RE_STARTERS_RE. Fixes #281.