use getKey helper instead of keypath.split() to get keypath key
remove let and default options to prevent bad transpilation
use fragment.toString() instead of (slower) fragment.getValue() with attributes where possible
fix Attribute$toString() for unrendered instances
separate fragment.getArgsList() from fragment.getValue()
remove unused determinePropertyName
keypath perf tests
use separate escape/non-escape toString functions for fragments - easier for browsers to optimise
Merge pull request #1578 from ractivejs/refactor

Refactor