Elseif clause parsing - (no else if else yet)
Parsing of else-if with else
Tests for else-if node transforms.
Change test model builder to allow nested conditionals
Conditional resolver now handles nested conditionals
Add description of elseif to the readme
Parsing rules for question identifier aliases

Useage
[date: date_for_adoption, alias: date_for_adoption_or_birth]

Supports the following questions
* Date Question
* Multiple Choice
* Text Question
* Salary Question
Initial country answer model with failing parse spec.
Extract shared parsing behaviour of question elements into question superclass.
Parsing for country question.
Introduce data modules to Node Transformer

Node interpreter now takes an optional data module,
this is similar to existing plugins, except that
they will be available at Flow build time, opposed
to render time.

Monkey patching parslet was the least painful way
to do this, otherwise we would need to introduce a
notion of partially created Elements and have a
post-transformation step.
Interpolation for country answers

Also fix for text answer interpolation, and tests
for multiple choice answer interpolation.
Add description of country questions to Readme.