change Pry.view_clip() to optionally drop or include hex value.

change 2nd argument of Pry.view_clip() to accept a Hash of options
with two keys: max_length (default 60) and drophex (default false).

the custom printer proc's in lib/pry.rb clip the object shown to
look better visually. this change still supports that behavior but
also changes the default behavior to include the hex value in the
inspect output.

@rf- suggested supporting both (with & without hex) to be able to
keep printer proc's pretty but also support other code that's okay
with printing inspects that are hex-y.