Update facts API docstring
The pyinfra facts API. Facts enable pyinfra to collect remote server state which
is used to "diff" with the desired state, producing the final commands required
for a deploy.
+
+Note that the facts API does *not* use the global currently in context host so
+it's possible to call facts on hosts out of context (ie give me the IP of this
+other host B while I operate on this host A).
"""
import re
