Changing to AvroParquetOutputFormat.

As noted in [AvroWriteSupport](https://github.com/Parquet/parquet-mr/blob/parquet-1.4.3/parquet-avro/src/main/java/parquet/avro/AvroWriteSupport.java), the AvroWriteSupport class shouldn't be used by users, instead the [AvroParquetOutputFormat](https://github.com/Parquet/parquet-mr/blob/parquet-1.4.3/parquet-avro/src/main/java/parquet/avro/AvroParquetOutputFormat.java) should be used in place of the ParquetOutputFormat. This change solves a ClassNotFoundException thrown on Hadoop 2.4.0:

```
14/07/07 20:31:53 INFO Configuration.deprecation: mapred.output.value.class is deprecated. Instead, use mapreduce.job.output.value.class
14/07/07 20:31:53 ERROR executor.Executor: Exception in task ID 1043
parquet.hadoop.BadConfigurationException: could not instanciate class parquet.avro.AvroWriteSupport set in job conf at parquet.write.support.class
        at parquet.hadoop.ParquetOutputFormat.getWriteSupportClass(ParquetOutputFormat.java:121)
        at parquet.hadoop.ParquetOutputFormat.getWriteSupport(ParquetOutputFormat.java:302)
        at parquet.hadoop.ParquetOutputFormat.getRecordWriter(ParquetOutputFormat.java:262)
        at parquet.hadoop.ParquetOutputFormat.getRecordWriter(ParquetOutputFormat.java:252)
        at org.apache.spark.rdd.PairRDDFunctions.org$apache$spark$rdd$PairRDDFunctions$$writeShard$1(PairRDDFunctions.scala:712)
        at org.apache.spark.rdd.PairRDDFunctions$$anonfun$saveAsNewAPIHadoopDataset$1.apply(PairRDDFunctions.scala:730)
```