Revert "Update testing instructions in README"

This reverts commit 46b1cfd5a1fe95ce62daa26f4af49b0445844635.
Revert "Change Capybara Javascript driver from Webkit to Poltergeist"

This reverts commit 4445ab95c8ac5912afe37fd30bf0d1c5446cc1bd.
Fix BCrypt scoping issue in user model