Report Errors/Spikes to Rdio Scanner

[taclane]

API-compliant fix for Rdio Scanner to see transmission errors and spikes.

The Rdio plugin API takes the following input:

- frequencies - [optional] JSON array of objects for frequency changes throughout the conversation.
{
errorCount: number;
freq: number; // in hertz
len: number; // in seconds
pos: number; // in seconds
spikeCount: number;
}[];

Uploading errors/spikes to Rdio Scanner via the upload-script method should already work as of this branch. When parsing a t-r metadata file, r-s is expecting error_count and spike_count json keys which recent commits now provide.

[taclane]

This should address #602 as well as some of the comments in #635.