Use sqlite3-ruby 1.3.8, not 1.3.9

This fixes failing specs for rbx. For more details, see: https://github.com/sparklemotion/sqlite3-ruby/issues/122
platforms :ruby means MRI and Rubinius so we don't need :rbx

For more details on how to specify platform, see: http://bundler.io/v1.3/man/gemfile.5.html
Do not use test/unit for AR 4.1 tests
Do not override Mongoid::Criteria#page defined by scope

so we don't have to worry about runtime persistence. closes #326
Use the old hash syntax
rake spec:all should run spec:mongoid_40 as well
Allow failures for all mongoid 4.0 specs

It looks like #with option doesn't work right now. Since mongoid 4.0 is not
released yet, just allow them to fail for now. We'll come back later.
Do not include railties and rspec-rails gem [ci skip]

They are unneeded if Sinatra is used.
Test Kaminari::ActionViewExtension only when Rails is defined
Revert "Use SVG for status badges in README"

This reverts commit d1be2150f098abdb261b0cd752499c582b1f4262 because the badge
for travis doesn't show up correctly.
Merge remote-tracking branch 'upstream/master'