Fix issue #205 (history option to show just history for current session)
Add `--all` switch. `hist` is `hist --all` now. `hist` without any
parameters shows the history of the current session.
Make sure that `show-doc` displays the comments of the original
definition by default. This test *must* fail with current state of
things. The goal is to eliminate the oddities in Pry across some Ruby
implementations.
For more information see:
d05233ecd3
* removed most historicla junk from lib/pry/test/helper.rb
* relocated recalcitrant junk to the local spec/helper.rb (this isn't exposed to 3rd parties)