Compress large requests

- More efficient network usage
Fix changed file name (now called "pp-collector")
Make entrypoints bullet points
Add description of how to add new collector types
Run doctests in travis

This actually showed that one of the doctests was wrong.
Merge pull request #35 from alphagov/more-text-in-readme

Updates to README.rst
Remove errant print statement
Merge pull request #37 from alphagov/remove-errant-print

Remove errant print statement
Merge pull request #36 from alphagov/run-doctests-in-travis

Run doctests in travis
Merge pull request #19 from alphagov/compress-requests

Compress large requests
Allow the 'dataType' field to be overriden

The 'dataType' field in records predates data groups and data types. As
such they don't always match the new world order of data types. It's
fine to change in all cases other than Licensing which is run on
limelight, that we don't really want to touch.
Merge pull request #38 from alphagov/allow-dataType-override

Allow the 'dataType' field to be overriden
Refactor 'dataType' field overriding

It was hard to test where it was previously added.