PoParser::Parser

Fast parser directly using Crystal's powerful StringScanner

Important notes about StringScanner.scan:

• Scan will return nil if there is no match. Using the regex * (zero or more) quantifier will let scan return an empty string if there is "no match" as the empty string qualifies as a match of the regex (zero times). We make use of this "trick".
• The start of line anchor ^ is obsolete as scan will only match start of line.
• Ruby's (and by extension, Crystal's) regex is in single-line mode by default, therefore scan will only match until the next newline is hit unless multi-line mode is explicitly enabled.