upversion nokogiri and minor YARD tweaks
Don't farnarkle about with the Repository class when testing ASModel--use a temporary class instead.
added validation for end dates not being before start dates, and associated tests
added a test for incomplete ISO 8601 dates, tidied tests a bit and removed unnecessary time expansion from validation
Merge branch 'master' of github.com:hudmol/archivesspace into 41440365-begin-before-end-date-fix
do some of the tests against 'inclusive' date types - equivalent to 'bulk'
added a selenium test for end date before begin
fixed the json_date factory so that end dates aren't before begin dates
fixed tests broken by end before begin validation
made resource id_0 required and wrote tests for it
Merge pull request #237 from hudmol/41440365-begin-before-end-date-fix

41440365 begin before end date fix
Merge pull request #238 from hudmol/42268601-make-resource-id-0-required

made resource id_0 required and wrote tests for it
Initial support for storing enum values as links to a global enumerations table.

Uses foreign key constraints to make sure everything stays consistent.

Switched a couple of enums over to storing their values this way, with an eye
to having the JSON schemas pull their values from the enumerations table.
Split Enumeration class into its own file.
Add the ability to migrate all records from one enumeration to another
Added test cases for enumerations
New permission
Add a new 'dynamic_enum' schema type that looks to the JSONModel's enumeration source for its possible values.
MemoryLeak rejigging
Added controller for querying enumerations