Add test coverage and remove condition from ShowBreadcrumb

This commit adds a spec for both the HasBreadcrumb and ShowBreadcrumb
modules.  In order to enable tests to run considerable support assets
have been added including, models, gem dependencies, and the Rails
framework.

The reason for the test support files is because this gem extends
ActiveRecord models via mixing these two modules.  This means in order
to test the expected behavior a full working ActiveRecord environment is
required.  This is achieved by including Rails and building up a partial
app via the /support directory.

In addition to the test coverage, a condition in the ShowBreadcrumb
module was found to not be required.  Therefore it was removed.

Lastly, the README was touched up to better word the functionality of
this gem.
Move ActiveSupport on_load methods into spec helper

This commit moves the ActiveSupport on_load methods into the spec helper
so that they will not conflict with the host rails environment.  These
methods are only needed when running the test suite.
Load has_breadcrumb at runtime

This commit removes the need for the has_breadcrumb initializer by
instead loading up the has_breadcrumb modules when the gem is loaded.
Place initializer code into railtie class and edited README

This commit moves the initialization of the has_breadcrumbs modules into
a railtie class which removes the necessity of using an initializer in
the hosting application.

Also updated was cleaning up a few sentences in the README.
Add condition to handle single crumb objects

This commit re-introduces a condition on show_breadcrumb that handles
cases where there is only one crumb. This would occur if there were no parent objects.

In this case the object would be return with a top level link pointed to
the object's resource.
Refactor ShowBreadcrumb implementation and specs.

Switch to modern "expect" syntax for rspec in the specs. Rename
`lookup_breadcrumbs` to `collect_crumbs` to better explain what it does.

[8212]
Update gemspec author and added ActiveSupport and ActiveRecord as dependencies.
Update has_breadcrumb to modern syntax and to be self documenting.

Started using in file classes to document the usage of the
has_breadcrumb method so that you can see it and understand right there
instead of using the packaged models. Cut those specs run time by 80%
and improved understanding when reading the tests.

[8212]
Merge pull request #2 from sqm/8212-convert-sqm-breadcrumb-into-a-gem

#8212 -  Convert sqm breadcrumb into a has_breadcrumb gem