Escape character in string breaks syntax coloring

[Zylann]

A sequence like this causes the rest of the file to be considered a string:

    for i in len(symbols):
        symbols_regex_string = str(symbols_regex_string, "\\", symbols[i])
    symbols_regex_string += "]"
    _symbol_regex = RegEx.new()
    _symbol_regex.compile(symbols_regex_string)

And in fact, even Github fails on this, but Github's coloring isn't great either^^

[PrestonKnopp]

This should now be fixed with: 3e4b8e1.