Global view context.

Updates `vision` to version `1.2.0` in order to provide the ability to specify a global  view context that is merged with any context values specified on the handler or via `reply.view()`. When merging, the global context values always have lower precedence than other context values. The global value may be either a context object or a function that takes no arguments and returns a context object. If a function is provided, it will be evaluated on each request before merging with other context values.
- - -
Specifying
```
server.views({
    context: {
        version: '1.5.5',
        name: 'Application Name',
        type: 'global'
    }
});
```
and then calling
```
reply.view('index', {
    test: 'This is the index view.',
    type: 'local'
});
```
results in a context object of
```
{
    version: '1.5.5',
    name: 'Application name',
    test: 'This is the index view.',
    type: 'local'
}
```
- - -
Specifying
```
server.views({
    context: function () {
        return {
            version: '1.4.5',
            date: Date.now(),
            type: 'global'
        };
    }
});
```
and then calling
```
reply.view('index', {
    test: 'This is the index view.',
    type: 'local'
});
```
results in a context object of
```
{
    version: '1.4.5',
    date: <timewhencontextruns>,
    test: 'This is the index view.',
    type: 'local'
}
```