dillon1000/react

Support AssignmentPattern (default values in destructuring)

"Supports" default values in destructuring (AssignmentPattern) by lowering to a 
ternary, even in the output. Examples: 

```javascript 

// Input: 

const [x = 'default'] = y; 

// Output: 

const [t0] = y; 

const x = t0 === undefined ? 'default' : t0; 

``` 

```javascript 

// Input 2 

const [{x} = makeObject()] = y; 

// Output 2 

const [t0] = y; 

const {x} = t0 === undefined ? makeObject() : t0; 

``` 

Note that this is how Babel lowers AssignmentPattern, so it isn't too bad. This 
should help avoid the need to update product code, even if the output isn't 
perfectly ideal.