Fix from_string when the port is not specified

[asv]

Before fixing:

Eshell V5.10.1  (abort with ^G)
1> uri:from_string("http://test.com").
** exception error: bad argument
     in function  integer_to_list/1
        called as integer_to_list([])
     in call from uri:port_to_string/1 (src/uri.erl, line 459)
     in call from uri:to_iolist/1 (src/uri.erl, line 562)
     in call from uri:update_raw/1 (src/uri.erl, line 558)
2> 

[ericbmerritt]

(Dead code elimination) e3de4a5 should be squashed with e2a56c3 (fix from_string when port is not specified)

[ericbmerritt]

Other then that, this looks pretty good.

[asv]

Sorry for bad pull request. I will go to refactor it and split up into multiple pull requests. Each of which belongs to it's own topic branch.

[ericbmerritt]

@asv you can do that if you like. I am much more worried about small, consistent focused commits then I am about separate pull requests. In the end its the commits that matter most.