Make TRUST_ENDPOINTS_FOR_REQUESTS take hostnames instead of URLs

[Pwuts]

If you put e.g. 192.168.1.42 into TRUST_ENDPOINTS_FOR_REQUESTS, it doesn't work because urlparse can't parse URLs without a schema. So instead of converting from URL to hostname in Requests.__init__, we should just make TRUST_ENDPOINTS_FOR_REQUESTS a list of hostnames rather than URLs, and also probably rename it to TRUSTED_HOSTS_FOR_REQUESTS.