Make timeout configurable for all HTTP calls

[eschizoid]

Rather than hardcoding the timeout (3 seconds), seems like a good idea to make this parameter configurable depending on the client needs.

[jrudio]

You can change it by accessing Plex.HTTPClient.Timeout directly. Like so:

plexConn, _ := plex.New("abc", "123")

plexConn.HTTPClient.Timeout = time.Minute * 1

But yeah, what's the best way to change the parameters? Like just add an extra argument? plex.New("abc", "123", 1 * time.Minute)

[eschizoid]

@jrudio Not sure if it would be useful to just allow clients to configure the timeout. What you think about allowing clients to pass the whole http.Client reference?