Fix to the public api for missing elements

If an outcome or question was missing an element
we were blowing up, when it is actually legal to
have them missing. Now return nil instead.
(This was the behaviour before 0.11.0)
version bump to 0.11.1
Stop using fixed date for .gemspec
Merge pull request #113 from alphagov/stop-using-fixed-date-for-gemspec

Stop using fixed date for .gemspec
Merge pull request #111 from alphagov/fix_missing_elements

[MERGE FIRST]Fix to the public api for missing elements
Merge pull request #112 from alphagov/version_bump

[MERGE SECOND] version bump to 0.11.1
Adding require dependancies so associated tests can run in isolation

require 'parslet'
* Parslet::ParseFailed

require 'smartdown/parser/node_transform'
* Smartdown::Parser::NodeTransform.new.apply(.....

require 'smartdown/parser/predicates'
* Smartdown::Parser::Predicates.new.parse(....
Redirect to outcome when extra URL parameters entered after outcome