add basic preceding_text option to breadcrumbs
only shows preceding text if there is available breadcrumb
added support for :join_with to links

Footer navigation elements should be joinable with custom separation (e.g. " | ").
Fixed incompatibility with Gretel

Gretel stubs out controller.controller method to return nil. I've made a workaround for that. All tests pass.

It might have been a better idea to do:

	context.try(:controller) || context

... instead of the code I've written, but it breaks a lot of tests, which it should not.
added spec for :join_with behaviour to links_spec.rb
Merge pull request #101 from a0903638/master

add support for :join_with to links
Merge pull request #102 from SkyWriter/master

return context if context responds to controller, but returns nil (Gretel incompatibility)
rename :preceding_text option to :prefix
Merge pull request #100 from rodrigomanhaes/preceding_text

Add support to prepend text to breadcrumbs (prefix)
. update CHANGELOG for 3.8.0
Version bump to 3.8.0
. updated README (copyright)
. gemspec for version 3.8.0
render_navigation passes block to config.items
add spec to check that block passed is executed
add documentation for render_navigation
. CHANGELOG
Version bump to 3.9.0
. preparing for 3.9.0
we should not highlight items that are only partial matches.