chore(regexp-assemble): make README man page compatible
chore(regexp-assemble): make README man page compatible

Cleans up the syntax of and changes nesting in README to allow for
tools like ronn (https://github.com/rtomayko/ronn) to generate man page
formatting. That way, @RedXanadu can view the README in the terminal ;)

coreruleset/coreruleset,coreruleset/coreruleset,coreruleset/coreruleset,coreruleset/coreruleset,coreruleset/coreruleset,coreruleset/coreruleset