Update README.md

Merge pull request #28 from marcelbuesing/expose-enum

Remove public set_connection_mode function.

Update changelog for TLS client options in mqttc.

More detail on TLS errors in example mqttc.

Merge branch 'example-client-cert' of https://github.com/marcelbuesing/mqtt-async-client-rs into master

bin/publish runs cargo test with feature "websocket".

v0.3.0

Docs on ClientBuilder to include default TCP ports, mention feature websocket.

Add bin/integration-tests, add it to release process.

Update build scripts to test new feature "websocket".

Add tls client certificate parameters to example

Set default port based on connection type

Add websocket secure tls configuration and use of urls for building a connection

Remove comment that accidentally got left in