Update README.rdoc

clarify that paginate_array does not work on the array inline, but instead returns a new PaginatableArray.
Use instance variable in paginate_array example from #515

https://github.com/amatsuda/kaminari/pull/515#issuecomment-35795767
Use SVG for status badges in README

http://shields.io/ provides many standardized badges for OSS. The PNG versions provided by Shields are similar to the images currently used, but the SVG versions added here are more legible on high pixel density displays.
Test activerecord ~> 4.0.0 in active_record_40 gemfile

This changes from using '>=' which would install the latest version of
activerecord available at the time of running `bundle install`.
Support testing activerecord 4.1 from git.

This could be changed once Rails 4.1 is released to use rubygems, but it
might also be interesting to test against the stable branch for
regressions.
Remove tilt dependency since it's already required upstream
Test kaminari against Ruby 2.1.1
Merge pull request #517 from seanlinsley/patch-1

Use SVG for status badges in README
Refer ActiveRecord::Base from top level namespace
Merge pull request #522 from yuroyoro/arbase_refer_from_toplevel

Refer ActiveRecord::Base from top level namespace
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.