Remove the transaction block for rollbacks

The individual deletes will be in their own transaction but to keep
the transactions small do not group them together
Merge pull request #186 from bitzesty/remove-transaction-rollback

Remove the transaction block for rollbacks
Check failures upfront - before downloading updates
Merge pull request #187 from bitzesty/checking_failures

Check failures upfront - before downloading updates
Revert "Merge pull request #185 from bitzesty/remove-transactions"

This reverts commit b3d3070dff7664d851a83bf0f632a50a34f8c7ff, reversing
changes made to 7f7ae120f32fc65a084925fa787b79b9f301a6fa.
Revert "Merge pull request #186 from bitzesty/remove-transaction-rollback"

This reverts commit 7da2f97c861296a6e12019d6dcb3ed9b9be273b7, reversing
changes made to b3d3070dff7664d851a83bf0f632a50a34f8c7ff.
Change dates in integration specs
Redis related cleanup for test suite
Merge pull request #188 from bitzesty/bring-back-transactions

Bring back transactions as failures were due to high load on the mysql instances, once the infrastructure changes we should be able to sync with transactions (one per file).
Rabl caching with memcache in production env

This improves performance of the template generation of the JSON
Implements caching on the headings and commodities
Adds an expiry time for the caches
We need to set the key explicitly as we need the actual_date to
form part of the cache key

use memcache store

either set ENV["MEMCACHE_SERVERS"] if not localhost or change
cache_store's second argument to provide the location of memcache.

Sets global expires_in to 1 day.
Merge pull request #151 from alphagov/rabl-caching

Rabl caching
Set defaults for rollback to delete records. Add columns that hold error stacktraces
Fix rollback table.

According to the latest changes in rollback script.
README update
Use correct dates during rollback
Fix rollback related specs

Conflicts:
	spec/integration/tariff_synchronizer_spec.rb