Leverage namespace package

[reyang]

Please refer to census-instrumentation/opencensus-python#445 and census-instrumentation/opencensus-python@ff80d11.

We would want to have all the integrations following the same pattern:

1. Package name: opencensus-ext-memcached.
2. Namespace: opencensus.ext.memcached.

[odeke-em]

Thanks for filing this issue @reyang! Unfortunately this isn't a Python project, it is a Java project :)

But also currently this project is published on Maven Central https://mvnrepository.com/artifact/io.orijtech.integrations/ocspymemcached under my namespace.

[reyang]

Ah, sorry! I was looking at https://pypi.org/project/ocpymemcache/.