Hurl "Host" request header with port 8000

[jcamiel]

When performing a GET on localhost:8000, Hurl set the Hostrequest header to localhost whereas curl set this header to localhost:8000.
Hurl should be aligned with curl and set the Host header to localhost:8000.

There is an integration test on the subject:

hurl/integration/tests/headers.py

Line 9 in 3d2d9e3

assert request.headers['Host'] == 'localhost'

[fabricereix]

this is fixed by #21