Revert "Always set up Bundler"

[jasonrclark]

Reverts #1189

[PragTob]

.@jasonrclark from over at #1189 (for less jumping):

Turns out this was a very, very bad idea. This makes it so shoes won't execute from a directory that doesn't have a Gemfile with shoes in it, which is definitely not what we want.

Will need to just look harder at this to resolve more systematically for #1148 later but gonna revert for pre5

I personally have no idea why that'd cause it (unless we need the bundler code anywhere else, in which case maybe bundler should be an explicit dependency) - but for now Jason deserves some sleep and I go to work :)

[jasonrclark]

The problem is that require 'bundler/setup' patches things such that Bundler will restricts where code can be required from to just what's in your Gemfile. If you've got a Gemfile, that's exactly what you want. But if you don't--say you're just running the shoes executable on a file somewhere--this blocks you from actually loading the rest of shoes!

Not to self-promote too much, but actually have a lightning talk on how this works at pdx.rb a while back. Hopefully explains in a little more detail how that happens 🎥