rubico/x/ternary

must use `switchCase`

### ternary
like `switch`, but takes exactly three functions sans array
```javascript
y = ternary(ifFunc, doFunc, elseFunc)(x)
```
`ifFunc` is a predicate function that determines execution of `doFunc` or `elseFunc`

`doFunc` is a function that is executed on `ifFunc` truthy

`elseFunc` is a function that is executed on `ifFunc` falsy

y is either `doFunc(x)` or `elseFunc(x)` depending on `ifFunc(x)`

```javascript
const isOdd = x => x % 2 === 1

ternary(
isOdd, () => 'odd',
() => 'even',
)
```

TODO
* [ ] - [documentation entry](https://github.com/a-synchronous/rubico/tree/master/x#documentation)
* [ ] - implementation + tests