fix(package.json): fix repository url
fix(demo): correct demo of `translate-values`
feat(service): add possibility to translate a set of translation ids

This enriches both `$translate()` and `$translate.instant()` with the
possibility to call them with an array rather than a string. This makes
the API more comfortable in some situations.

```javascript
// for example...
$translate(['FOO', 'BAR']).then(function(translations){
  console.log(translations.FOO);
  console.log(translations.BAR);
});
// ... and
console.log($translate.instant(['FOO', 'BAR']).FOO);
console.log($translate.instant(['FOO', 'BAR']).BAR);
```
feat(directive): add option to define a default translation text

This adds an optional opt-in feature:

```html
<span translate=„my.key.for.a.welcome.message“ translate-default=„Welcome {{username}}!“></span>
```

or even

```html
<span translate translate-default=„Welcome {{username}}!“>my.key.for.a.welcome.message</span>
```
Update autogenerated documentation on how $translate is used
fix($translateProvider): fix comparison in one case of negotiateLocale()
tests($translateProvider): add test for locale negotiation w/o aliases
fix(service): docs annotation