Remove references to dialogs project.

soundcloud/dialogs.git is a nonexistent repo. I removed references to it
from .gitmodules and Makefile as well as removing vendor/dialogs. There
seems to be dialog code in src/sc/dialog.coffee.

Fixes Issue 2.
Fix tests.

Running the tests on a port other than 80 used to fail du to the use of
window.location.hostname. I changed it to window.location.host so the
correct port is used. I had to also change a line in
src/sc/dialog.coffee so the port is not used for the request to
soundcloud.com.
Keep the current window's protocol.

Instead of always using http for relative requests it makes more sense
to use the current window's protocol.