Switch data source to ta_path

[Nate-Wessel]

Resolves #182

[Nate-Wessel]

Want to now compare a bunch of random requests and make sure there's no systematic bias in either direction. I don't expect any.

[Nate-Wessel]

To compare the results of the two branches:

WITH ta_path AS (
    SELECT
        uri_string,
        (results->'results'->'travel_time'->'seconds')::real AS seconds
    FROM nwessel.cached_travel_times
    WHERE commit_hash ~ '5b8f'
), 

ta AS (
    SELECT
        uri_string,
        (results->'results'->'travel_time'->'seconds')::real AS seconds
    FROM nwessel.cached_travel_times
    WHERE commit_hash ~ 'fd2a'
)

SELECT
    exp(avg(ln(ta.seconds / ta_path.seconds)))
FROM ta
JOIN ta_path USING (uri_string)

Average difference so far looking like ~1%. Can test this further by just running more of the same queries on each commit.