Megatest (minimally) now working in Rails 4

Upgrades Megatest for Rails 4 (tested with Rails 4.1.0.rc2, Ruby 2.1.0-p0, Debian Linux).

Now, to run Megatest, just do:

$ bundle exec rake megatest

At this time, Megatest includes (only) a single RailsApp. (That app is rails-omnitest.)

Megatest can provide—and is close to providing!—a safer environment for hacking on gem, rac. Presumably, this gem's usefulness would be further increased (in ways both visible and unforeseen) if more people could improve the gem safely.

Simply following the steps (below) would include those Rails 4 apps that aren't (so far) in Megatest.

Unfortunately, I cannot devote any more time now to Megatest. However, regarding each additional Rails 4 app, someone else might simply:

1.)  Add its name to file, megatest/bash_scripts.rb, under CREATE_REPOSITORY_LIST_SCRIPT near "rails-omniauth";

2.)  Duplicate (and rename) these files in directory "megatest/config":

- rails-omniauth.yml</li>
- rails_omniauth_testing_recipe.rb</li>

3.)  In these duplicated files, make any changes (such as adding preferences) that are necessary for the Megatest to continue working—in order to increase its effectiveness, if you will! :)

Regarding newly added preferences, please see as well the other changes in this commit.

Also, of course, as a routine step, before committing any (other) changes to the gem, running Megatest can help everyone to test those changes—as well as help to keep Megatest working well.