continue ember-dev cycle fixes, and also bump ember-dev
Rename none/empty to isNone/isEmpty variables

Rename none ti isNone and empty to isEmpty variables. It makes the code
easier to read.
Merge pull request #981 from karlguillotte/master

Rename variables none/empty to isNone/isEmpty
Ignore 'docs/node_modules'

`yuidoc` is installed into this directory.
Avoid incorrect tag warning

```
warn: (docparser): replacing incorrect tag: returns with return:
```

I rewrite `returns` -> `return`.
Merge pull request #985 from tricknotes/avoid-incorrect-tag-warning

Avoid incorrect tag warning
Merge pull request #984 from tricknotes/ignore-node-modules

Ignore 'docs/node_modules'