Fix inconsistent buffer sizes sent to analyzer

The analyzers are sent new buffers of audio data to process each time
they pass through the gst pipeline. Different file formats and bit depths/
sample rates can change the size of these buffers, in some cases making them
large and therefore infrequent. This causes choppiness in the analyzer
as it is not getting new data with every frame. This patch chunks the buffers
coming off the pipeline to correspond with the framerate of the analyzer.

This is an example of the issue this fixes. Note the blockiness of the analyzer.
![screenshot from 2014-04-27 11-39-34](https://cloud.githubusercontent.com/assets/4623333/2836989/62ce1c7e-d00b-11e3-9a15-ff88445de3bd.png)