encode strings to utf-8 in ServiceInfo

[jgrill]

I found that properties dict values registered as "False" rather than the intended string value, such as "path" in the provided examples.

eg.

Service Paul's Test Web Site._http._tcp.local. added
Type is _http._tcp.local.
Address is 10.0.1.2:80
Weight is 0, Priority is 0
Server is ash-2.local.
Properties are
path: False

[coveralls]

Coverage decreased (-0.2%) when pulling c2f05f1 on jgrill:master into 05c3c02 on jstasiak:master.

[jstasiak]

Thanks for the contribution. I fixed it in f3fd4cd while refactoring the code. Feel free to reopen if it doesn't work for you for any reason.