Try rbx-2 on travis

According to https://github.com/travis-ci/travis-ci/issues/2230#issuecomment-42742477, we should use rbx-2 for now.
fix a bug where :view_paths wouldn't be inherited to nested helpers. added a stronger test.
Merge pull request #553 from apotonick/views-prefix

Fix a bug where :view_paths wouldn't be inherited to nested helpers.
Fix wrong travis config
Use padrino helpers ~> 0.11.0 if Ruby version is 1.8.7
Try using minitest on rbx instead of rubysl-test-unit
Do not run specs against AR 3.2 and older and Ruby head

I don't think they'll be supported.
AR edge is stable! :sparkles:
Fix a bug where the friendly url for the first page is broken

fixes #554
Use minitest on rbx against specs for mongoid 2.4
Do not allow the specs for mongo_mapper/mongoid 2.4/rbx to fail on travis
Revert "AR edge is stable! :sparkles:"

This reverts commit 5f7c5a27c9d3ea20f865cd2ded9111c9e5096144.

Conflicts:

	.travis.yml
oops :fire:
Tweak gemfiles and tavis.yml
Stick to RSpec 2.x for now...
How could the specs be run without rspec gem being bundled??
Use the stable rspec release (but still not 3.0...)
Update docs badge in README

Update the URL of the docs badge to include it from inch-ci.org instead of inch-pages.github.io (the former being the successor of the Inch Pages project).
Merge pull request #563 from rrrene/patch-2

Update docs badge in README [ci skip]
"DEPRECATION WARNING: Passing a string to ActiveRecord::Base.establish_connection for a configuration lookup is deprecated, please pass a symbol (:test) instead."