Prevent access to raw events

@pbadenski
@gtrogers
Prevent time-span being used to find individual events

@pbadenski
@gtrogers
Pull out validator class
Pull out validator super class
Pep-8 appeasment
Temp
WIP further refactoring, pulled out matcher
Something something wip
WIP (pulled out seven day time span validator)
Refactored all current methods
Delete giant static dict
Deleted unused methods for validation
Add validation for start_at and end_at on mondays

@maxfliri
@gtrogers
Treat fake dates as invalid
Pep8
Tidy unit tests for raw data queries.
Tidy up query parameter validations
Merge pull request #46 from alphagov/prevent_access_to_raw_events

Prevent access to raw events