compute lazily (see #1293)
fix weird bug that affects the test suite
test for lazy computations
tidy up applyChanges
viewmodel.compute() now creates a new computed value - viewmodel.init() does initial setup instead
remove Evaluator, use Computation instead
last few failing tests
remove references to evaluators, e.g. in viewmodel.register()
clear cache on computation init, dont mark
reset this.changes at the correct place
fix last failing test
remove unused diff.js
robustify keypath capturing logic
check dependencies have changed before recomputing values
linting
remove reference to unused priority properties
Merge pull request #1312 from ractivejs/lazy-computed

Lazy computed properties