Improve tolerance of :uri parsing to connect

[reify-james-vickers]

Currently protojure.grpc.client.providers.http2/connect requires a very specific format for :uri and does not accept some that it perhaps could. The URI's it seems to accept have scheme as well as port number, e.g. http://localhost:8080. Any piece missing makes the parsing fail, sometimes with a relatively opaque exception. It would be helpful for instance to support formats like:

• http://some-host or https://some-host, using the default port numbers for these protocols (i.e. 80 for http and 443 for https)
  • Currently omitting the port number causes an exception: (NumberFormatException) at java.lang.Integer/parseInt (Integer.java:614): null
• some-host.com or similar URI's that omit the connection protocol; not clear if it's really necessary to have the protocol or if it can default to something like https or correspond to what :ssl is defined/provided as.

[ghaskins]

Yeah, this has bugged me for a while, too. Just never got around to fixing it. PR welcome.

[reify-james-vickers]

#137

Found it a bit harder to support something like "something.com" with no scheme because lambdaisland/uri apparently won't read a host from that, doesn't seem too important anyway.