Add jsx:test task to defaults

Fixes #110 

## Problem

The supported 'jsx' language option does not come with a default task that will transpile .jsx in ./test to ./build/test

## Solution
Add new default task `jsx:test`

## How to +10

- Include a .jsx file in ./test
- `gulp test` should result in that file being transpiled into ./build/test with a `.js` extension

@trentgrover-wf 
@evanweible-wf