Revert "Only run tariff sync once a day at 01:23"

This reverts commit b21cac649e2907a53784fb0f15fdf8ae08441552.
switch from `curb` to `faraday`

Moving to `faraday` because curb sometimes raises *Host Resolution Error*

[pivotal story](https://www.pivotaltracker.com/n/projects/488191/stories/69001522)
Merge pull request #162 from bitzesty/69001522-faraday

switch from `curb` to `faraday`
Retry downloading update if update file is missing

When Tariff runs in multiserver environment one server may have
downloaded the update and marked as pending. If other server tries to
apply it, it won't find the file. Therefore we try to redownload if file
is missing.
fix specs
Merge pull request #161 from bitzesty/65969536-download-missing-updates

Retry downloading update if update file is missing
Switch to redis-semaphore

Conflicts:
	spec/integration/tariff_synchronizer_spec.rb