Update inputrc to work with modern iTerm2

I'm not sure when things changed in iTerm2 or what exactly changed, but
as of iTerm2 3.5, I find that I need these mappings in order to get the
behavior described in the comments.

inputrc

@@ -1,7 +1,7 @@
 # Configure option + right arrow to move forward one word in iTerm2
 # https://www.gnu.org/software/bash/manual/bashref.html#Commands-For-Moving
-"\e\e[C": forward-word
+"\e[1;3C": forward-word
 
 # Configure option + left arrow to move backward one word in iTerm2
 # https://www.gnu.org/software/bash/manual/bashref.html#Commands-For-Moving
-"\e\e[D": backward-word
+"\e[1;3D": backward-word