'.'        Dot, matches any character
'^'        Start anchor, matches beginning of string
'$'        End anchor, matches end of string
'*'        Asterisk, match zero or more (greedy)
'+'        Plus, match one or more (greedy)
'?'        Question, match zero or one (non-greedy)
'{n}'      Exact Quantifier
'{n,}'     Match n or more times
'{,m}'     Match m or less times
'{n,m}'    Match n to m times
'[abc]'    Character class, match if one of {'a', 'b', 'c'}
'[^abc]'   Inverted class, match if NOT one of {'a', 'b', 'c'}
'[a-zA-Z]' Character ranges, the character set of the ranges {a-z | A-Z}
'\s'       Whitespace, '\t' '\f' '\r' '\n' '\v' and spaces
'\S'       Non-whitespace
'\w'       Alphanumeric, [a-zA-Z0-9_]
'\W'       Non-alphanumeric
'\d'       Digits, [0-9]
'\D'       Non-digits
'\xXX'     Hex-encoded byte
'|'        Branch Or, e.g. a|A, \w|\s
'(...)'    Group

Mini regex-module [1] inspired by Rob Pike's regex code [2]

The limits below determine the static RAM usage of this library.

Max number of regex symbols in expression: 30
Max length of character class buffer:      70

[1] tiny-regex-c
<https://github.com/gyrovorbis/tiny-regex-c>

[2] Beautiful Code
<http://www.cs.princeton.edu/courses/archive/spr09/cos333/beautiful.html>
