Remove type check when adding callback to Observable
Change spec of Observable

Callbacks required to be called with new and old values.
Update Observable to call callbacks with new and old values
Change Observable spec: use o.value, not o.get()
Change ObservableNumber spec: use o.value, not o.get()
Update Game spec to reflect changes in Observable spec
Update Scorecard spec to reflect changes to Observable spec
Update ScorecardStorage spec to reflect changes in Observable spec
Update implementation files to reflect changes to Observable spec
Revert to relative ‘require’ paths to satisfy Browserify

Browserify doesn’t play nice with ‘rekuire’ (which allows one to
‘require’ without a path). Relative paths it is :(
Add Fisher-Yates shuffle to utility module

lodash.shuffle has rather a lot of dependencies, given it’s only one
function
Add incomplete Controller class (to handle user input)
Add incomplete Mediator class
Add incomplete ‘main’ script
Add gulp ‘watch’ task to auto-run specs task