Exclude some spam paths found in UKTI logs
Ignore hits from TNA sending users back to a site
Speed up Whitehall mappings import

Until now, we have been loading the host for each old URL in the CSV from the
database each time. This manually caches the hosts.

In development this changed the runtime for:
➜  transition git:(master) ✗ time FILENAME=tmp/1396018394-whitehall_mappings.csv be rake import:whitehall:mappings

from:
FILENAME=tmp/1396018394-whitehall_mappings.csv bundle exec rake   181.65s user 112.01s system 88% cpu 5:31.37 total

to:
FILENAME=tmp/1396018394-whitehall_mappings.csv bundle exec rake   95.10s user 54.83s system 86% cpu 2:53.45 total
Exclude UKTI (possibly Wordpress) image paths
Merge pull request #234 from alphagov/speed_up_whitehall_import

Speed up Whitehall mappings import by 50%
Merge pull request #232 from alphagov/exclude_some_uninteresting_ukti_patterns

Exclude some uninteresting UKTI patterns
Merge pull request #233 from alphagov/ignore_hits_from_tna

Ignore hits from TNA sending users back to a site