Use new PyCBC json file for astro classification

PyCBC Live is developing a tool that computes relative probabilities of source types based on template chirp mass and effective distances. The probabilities are available for each G event as a json file and as a pie chart in the GraceDB page. We would like this json file to be read in by gwcelery, and processed through the standard p_astro code to add the terrestrial probability via the calculation already being done for PyCBC in lscsoft/p_astro.

Related issue: emfollow/gwcelery#340 (closed)