Exceptions thrown for "bad" input

"Illegal" input, such as word anchors (/\bWORD\b/.examples), will raise an IllegalSyntax error. These features will never be suported by the gem.

"Unsupported" input, such as POSIX bracket expressions (/[[:space:]]/.examples), will raise an UnsupportedSyntax error (as opposed to just giving "examples" that do not match!!). These features may, one day, be supported by the gem.