Overhaul

[lukateras]

I see that REPL is unmaintained for quite a long time.
So I’ve decided to fix some issues and to refactor REPL.

Key features of my commits:

• Trimmed down from 105 to 51 strings,
• Fixed all issues (Remove extraneous 'http://' in help message. #14, Customizing REPL_PROMPT #15, Improves custom prompt #16),
• Used optparse stdlib library,
• Made standalone installation fully workable,
• Added -v, --version flag,
• Added short form of flags — so you can repl -s ruby instead of repl --stdin ruby,
• Updated all documentation — both man and README.md,
• More helpful --debug — lists all parsed options,
• Now you can format REPL_PROMPT, insert %s where the name of program should be,
• Version is moved from lib/repl/version.rb to bin/repl so repl can be installed standalone,
• When installing standalone, man page installs too,
• Makefile added to install/uninstall standalone version (you can still stick with curl),
• Precompiling the pattern and just formatting it each time with STDIN.gets.chomp and precompiling the prompt is actually a little bit faster and cleaner.

@defunkt: if you don’t like some of my changes, just tell me and I revert it back.
I shall continue maintaining this repo if you don't mind.

To bump the version, look on line 22 of bin/repl.

[lukateras]

Nah, it will never be merged.

[pvdb]

@yegortimoshenko / @thedrow - FWIW: I have resurrected/forked @defunkt's original repo, and accept PRs at pvdb/repl ... there's an outstanding Homebrew PR that updates the repl formula to point to my fork, which should hopefully get accepted/merged shortly.