IE 8 support
Replace Chai with Proclaim for IE 8 compatibility
Chrome 37.0.2062 --> 38.0.2125
INTEGRATE: IE 8 support

* dev:
  Chrome 37.0.2062 --> 38.0.2125
  Replace Chai with Proclaim for IE 8 compatibility
  IE 8 support
Exception checks in assertion library
Better error messages when exception assertions fail
'ensure.js' provides production code assertions
Type check assertions removed from ensure.js

Use ensure.signature() instead
Placeholder code uses new ensure.signature() call
Array.isArray() workaround for IE 8
Object.getPrototypeOf() workaround for IE 8
'watch.js' queues up build if changes made while building
INTEGRATE: Production assertions, improved tooling

* dev:
  'watch.js' queues up build if changes made while building
  Object.getPrototypeOf() workaround for IE 8
  Array.isArray() workaround for IE 8
  Placeholder code uses new ensure.signature() call
  Type check assertions removed from ensure.js
  'ensure.js' provides production code assertions
  Better error messages when exception assertions fail
  Exception checks in assertion library