Don't use Rake v11 with older rubies

It doesn't work with Ruby 1.8.7 and 1.9.2.

let request specs use integration test services

This allows request specs to call assert_select, url_for, etc.

Move #738 regression check to spec

This is confusing and not useful as documentation, all #738 was intended
to do was to prevent our let definitions from being defined earlier than
3rd party inclusions (and hence being overriden) which was confusing
behaviour, so move it to a spec.

Add readme for mailer specs

[skip ci]

Fixing index view tests for a scaffold with multiple float attributes

If a model has 2 float attributes, the auto generated
tests are failing ones because of duplicate value.

Add negated template examples

Move travis from using Rails 5 beta1 to using beta2.

Improve the documentation about automatic metadata

[skip ci]

[skip ci]

Prevent Rails 3.2.22.1 on Ruby 1.8.7

Fix performance regression with empty template rendering

Closes #1537.

The change in 80637fc9 introduced a performance regression because the
template lookup cache was being lost every time an example was run.

This commit fixes the problem by caching the EmptyTemplateResolver
instances between example runs in a hash indexed by the path string.

Fix empty template rendering for Rails 4.2.5.1

Closes #1532.

Refactor the template rendering overrides in controller specs to be more
compatible with the Action View public api. Previously `EmptyTemplatePathSetDecorator`
overrode the `find_all` method to wrap a path set. However `ActionView::PathSet`
is not public api so instead create a subclass of `ActionView::FileSystemResolver`
to return an empty template and treat `view_paths` as an array of string-like objects.

Use the same version of nokogiri in example app

This is because the security release of `3.2.22.1` was not correctly
tested against 1.8.7 which means that our build will not pass against
this ruby. /cc @pixeltrix.

... to fix the installation problem on Travis CI.

Do not leak TestUnit specific methods after Rails 4

Favor https: over git: protocol remotes