add avro schema to support other languages

Add [Apache Avro](http://avro.apache.org/) protocol schema for other [Supported Languages](https://cwiki.apache.org/confluence/display/AVRO/Supported+Languages).It was only a partial modification to the attempt. Not centain if such avro schema can fit this project.

```
$ nosetests test/test_avroproto.py
....
----------------------------------------------------------------------
Ran 4 tests in 0.002s

OK
```
I am feeling uneasy about the way the arguments are passed to `hello_json`. You are passing a set, which means identical values will get squashed. Perhaps you meant to pass a dictionary and use the `**` operator, like [this](https://docs.python.org/2/tutorial/controlflow.html#unpacking-argument-lists).

However, since the values of the dictionary match one-to-one with the arguments of `hello_json`, perhaps you should drop the set entirely and just call the function in the usual way.

Am I missing something?