Fixed about_regular_expressions.rb to pass tests

Learned about:
* regular expressions,
* using regex to search a string for matching content,
* meanings of ?, + and * when matching a string.

[#65851756]
Fixed about_regular_expressions.rb to pass tests

Learned about:
* the left most match that wins,
* various character classes,
* dot, that is a shortcut for any non newline char,
* negating a character class with ^ and capitals.

[#65851756]
Fixed about_regular_expressions.rb to pass tests

Learned about anchoring:
* to the start of the string,
* to the end of the string,
* to the start of lines,
* to the end of lines.

[#65851756]
Fixed about_regular_expressions.rb to pass tests

Learned about:
* vertical_pipe_that_means_or,
* #scan method that is like find all,
* #sub that is like find and replace,
* and #gsub that is like find and replace all.

[#65851756]