Fix issue #885 (Add an API for extending Pry.view_clip)
[1] pry(main)> class Barbie
| def inspect
| 'You can brush my hair, undress me everywhere!'
| end
| end
=> nil
[2] pry(main)>
[3] pry(main)> Pry.config.prompt_safe_objects << Barbie
=> [String, Numeric, Symbol, nil, true, false, Barbie]
[4] pry(main)> cd Barbie.new
[5] pry(You can brush my hair, undress me everywhere!):1>
Many plugins only define a puts method on the output object. This change
removse the ability to customize the formatter used when outputting
variables in `ls`. We should reconsider the best way to do this.
* 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)