Matching bracket/parenthesis highlighting

[kyrylo]

Moved from: pry/pry#283

Description by @jrunning:

A feature I'd love to see in any REPL is IDE-style bracket matching, i.e. as I'm typing or moving the cursor back and forth on the line, if the character under or adjacent to the cursor is a parenthesis or bracket its mate, wherever it is on the line, is highlighted in some way. This would be especially useful when composing and testing complex regular expressions. I don't know how difficult it would be to implement so I don't know how realistic my request is, but it would certainly help set Pry even farther ahead of the pack.

[Mon-Ouie]

I added this.

For the record, there are still things that can be improved:

• Properly handling strings, and other things that use the same characters for opening and closing (%w!foo bar!)
• Right now, this just inserts a "clear" code after the bracket; one could try checking the ansi codes that currently apply to make sure they aren't cancelled.