Remove / from route of TreeRedirectHandler.
Remove / from route of TreeRedirectHandler.

When base_url is set, navigating to http://{url}/{base_url} returns 404
This is due to the TreeRedirectHandler only picking up
http://{url}/{base_url}/ and the trailing slash handler being set to
{base_url}/.*/.

This change will cause http://{url}/{base_url} to correctly redirect to
http://{url}/{base_url}/tree, as expected.

ipython/ipython,ipython/ipython