This commit includes 2 things:
1. Sometimes (seemingly due to client caching), performance entries
aren't available, even for the currently executing script. This waits
until the first retrieval of 'CONSUL_HTTP_PROTOCOL' before using the
performance entries to decide this. This means that the entries aren't
inspected until ember has initialized, which means that the entries are
always available.
2. getCurrentResource/getResourceFor could potentially return undefined
if the correct entry could not be found. This adds a default {} return
value if the resource cannot be found. This means that if for whatever
reason the correct resource cannot be found at least we don't fail with
an error and just drop back to HTTP/1 functionality.
