Time decay boosting for content with a public timestamp

Implemented using a custom score as in this blog post:
http://jontai.me/blog/2013/01/advanced-scoring-in-elasticsearch/

Changed `now` to time() and have not included a general boot of +1 as
this is only applied to documents where the public_timestamp exisits.

Also had to increase the boosts on the Inside Gov formats to compensate
for the time boosts.

This is for: https://www.pivotaltracker.com/story/show/42780733
Comments on the time_boost
Added tests for time decay
After working through this with david - decided on changing this into a
boost (not a penalty) as then the relavency score for older documents
will get lowered as the boot value is multiplied.

The result is that we can then revert the boost values on inside gov
formats

We tweaked the values of the curve so the maximum boost will be 2 (for
documents published right now). And generated a new graph in days so
it's actually readable.
Link to the graph not just the formual

Boost value vs days
Merge pull request #57 from alphagov/time-stamp-boosting

Time stamp boosting on documents with a field public_timestamp
tweak tests after lowering public_timestamp boost
wait_until_ready should wait for green

This is because rerunning the tests will crash ES after a while - also
use the default timeout of 30.
Reorder the tests

Suspect the time boosting is not being applied
Increase sleep between runs.

Is CI configured with a different number of shards to the dev machines?
Fix tests: add_field_to_mappings to take a type parameter

Also make the dates valid for ES.
Synonym updates

Student finance etc, lots of forms/leaflets and misspellings
Merge remote-tracking branch 'origin/synonyms-20130212'

Conflicts:
	elasticsearch_schema.yml
Revert "wait_until_ready should wait for green"

This reverts commit 1554ea2ba1ade4789cee9d088dd53ed96c5ce717.