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)
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
Introduce tests around outcome and question api elements
0.11.2 version bump
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(....
Refactor
Redirect to outcome when extra URL parameters entered after outcome
Merge pull request #116 from alphagov/adequate_outcome

Redirect to outcome when extra URL parameters entered after outcome
Simplify intro text and provide a very simple example

- Thought it would be good to show any new users what the outcome of using the DSL would be
- Shows an image of the final outcome within a GOV.UK sample page
- Will break into more complex concepts around logic as we go.
*NB:* My intention is to move the majority of the 'node' logic examples to the [wiki](https://github.com/alphagov/smartdown/wiki) so this readme just provides an intro, installation, test and running guides. All further info around specific tasks can sit in the wiki.
Test for node api and fixes for return types / post body.
Merge pull request #114 from alphagov/fix_missing_elements

[MEGE FIRST] Fix missing elements
Merge pull request #115 from alphagov/version_bump

[MERGE SECOND] 0.11.2 version bump
Add link to the wiki

- Adding this quite high up as readers may just wish to get to the implementation details immediately, having seen the intro speil before.
Quick reweite of the language para

- very minor clarification of language, probably just subjective here!
Change the language from 'cover sheet' to 'start page'

- We have Start Pages on GOV.UK and I think everyone is familiar with this terminology
- Not sure if there's a separate language within content teams wherein 'Start Page' gets translated into 'Cover Sheet', but I think 'Start Page' works for a broader range of people within a team.
- Adds liknks to wiki entries for start pages and questions. Placeholders for the other types
Move 'cover sheet', 'question' and 'choice' to the wiki

- They're at https://github.com/alphagov/smartdown/wiki/Start-Pages, https://github.com/alphagov/smartdown/wiki/Questions and https://github.com/alphagov/smartdown/wiki/Choices now
- Have also been rewritten to include examples of smartdown, html and rendered content
Move scenarios to the wiki

- https://github.com/alphagov/smartdown/wiki/Scenarios
- Just a quick shift over to the wiki, more work can be done on the page there.