get readline support (ctrl+r etc) for Pry in OSX

See guard/guard#619 (comment)

Technically for OSX you don't need readline, and we'll focus on using
libedit which OSX comes with instead.

Edit the file .editrc in your home directory. Add this line:

bind "^R" em-inc-search-prev
You can now use ctrl+r to do a reverse history search.

Ref: http://hints.macworld.com/article.php?story=20080313113705760

Alternatively, install GNU Readline and get Ruby to use it:
https://github.com/guard/guard/wiki/Add-Readline-support-to-Ruby-on-Mac-OS-X

Finally, Pry does work with rb-readline, a pure Ruby implementation of
Readline which shouldn't suffer from the platform and install
dependencies of the standard Readline.
Ref: https://github.com/luislavena/rb-readline

.editrc

@@ -0,0 +1 @@
+bind "^R" em-inc-search-prev