Assertion if incrementProperty given non-numeric value

Includes fixes for incrementProperty and decrementProperty.

Ember.assert in incrementProperty and decrementProperty discourages any attempt to increment/decrement by a non-numeric value or Infinity.

Retains support for 0 increment

Added tests for NaN, non-numeric string, and Infinity
Aborts/redirects in willTransition don't enter LoadingRoute

Closes #3034. Closes #2987.
Merge pull request #3040 from realityendshere/increment-property-nan

Fix incrementProperty/decrementProperty to handle NaN
linkTo param of 0 should be treated as a url param

Part of this fix is in router.js, the other part in Ember.

`linkTo` was generating incorrect hrefs when the provided
parameter was the number 0 (even though '0') worked. Now it
will work as expected without requiring casting to a string
first.

Also removed some unnecessary code on Ember's side to check that all
bound params are truthy before reporting that `routeArgs` changed in
`LinkView`.
Clarified Ember.warn message for linkTo loading state
Removed old-router
Clearer messaging for  changes and removal of bad assert
Fixed minor type of  to be , as both correctly spelt and referenced elsewhere in the surrounding comments
Merge pull request #3074 from jdjkelly/master

Fixed minor type of  to be , as both correctly spelt and referenced else...
adding docs for observers
Fix some docs
Update view.js

Fixes docs: several calls to Ember.View.create() changed to Ember.View.extend()
router.js sync - don't overwrite URL's on noop transitions

See here for more info:
https://github.com/tildeio/router.js/commit/6254eae384ae378373e3e1a86f7c9abd0c0455af
Make methods on the router overridable. Denote private methods with _
Components should not be singleton (just like views)
Merge pull request #3073 from alexspeller/make-setupRouter-public

Make methods on the router overridable
Merge pull request #3078 from nofatclips/master

Update view.js
removing line that mentions value
Fix yield helper to only be craycray for components
Merge pull request #3077 from twokul/master

adding docs for observers