Avoids double slash at start of paths when mounting an engine at the root.

This fixes a bug that is caused by Resource/SingletonResource mangling resource options when using inline "multi"-resource declarations.

When format is true, it is mandatory (as opposed to :format => false).
This is currently not possible with resource routes, which automatically
make format optional by default.

This fixes a bug that is caused by Resource/SingletonResource mangling resource options when using inline "multi"-resource declarations.

When format is true, it is mandatory (as opposed to :format => false).
This is currently not possible with resource routes, which automatically
make format optional by default.

addresses issue #1907 - any routes that follow a route with a constraints
  block are inheriting the previous route's constraints.

Previously it was:

    {:controller=>"photos", :action=>"show", :id=>/[A-Z]\d{5}/}

Now it becomes:

    photos#show {:id=>/[A-Z]\d{5}/}

Update the description of the :path option to #resources to reflect that it sets the actual path, not a prefix. Most instances were already fixed.

After a long list of discussion about the performance problem from using varargs and the reason that we can't find a great pair for it, it would be best to remove support for it for now.

It will come back if we can find a good pair for it. For now, Bon Voyage, `#among?`.