clean up TranslateableProperties spec

No reason to have two describe blocks.
eachTranslatedAttribute gracefully handles null translation keys

If an object has a `___Translation` key that points to a null value,
`eachTranslatedAttribute` will call the callback with `null` instead
of trying (and failing) to get a translation.

Closes #150
Merge pull request #167 from jamesarosen/james/null-translateable-property

eachTranslatedAttribute gracefully handles null translation keys
Changelog: fix typo
add .editorconfig
v3.0.0-beta.1
Relax Handlebars constraint to 1.x, 2.x

Ember 1.8- use Handlebars ~1.0. Ember 1.9+ will rely on
Handlebars 2.0+. To support both, we need both the 1.x and 2.x series.
Specify ember dependency with ~ notation
v3.0.0-beta.2
Current beta uses Handlebars 2.0.0
Travis: Ember beta uses Handlebars 2.0.0
Document bound keys with {{t}} helper
Add pluralization example
Merge pull request #176 from vaclavbohac/doc-pluralization

Add pluralization example
Using Ember.get for interpolations

For the following strcutured interpolation functionality:
   {{t "User {{contact.firstName}} {{contact.lastName}}" contact=xxx}}

While till this patch this has to be done as follows:
   {{t "User {{firstName}} {{lastName}}" firstName=xxx.firstName lastName=xxx.lastName}}
Merge pull request #177 from opichals/use-em-get-for-interpolations

Using Ember.get for interpolations
Ember "release" version now requires Handlebars 2.0.0
Test against Ember 1.7.1, Handlebars 1.3.0

Now that more recent Ember versions are moving to HTMLBars and
Handlebars 2.0, we need to add a test to ensure we maintain
backwards compatibility.
Merge with upstream to align