fix: shelljs exec usage, part 2 (#32)

`output` was replaced with `stdout` in shelljs 0.6.0.

lib/simctl-extensions.js

@@ -22,6 +22,7 @@ OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 THE SOFTWARE.
 */
 
+
 const shell = require('shelljs')
 const path = require('path')
 const fs = require('fs')
@@ -36,7 +37,7 @@ const extensions = {
     const res = shell.exec(command, { silent: true })
 
     // parse output for Xcode version
-    const versionMatch = /Xcode (.*)/.exec(res.output)
+    const versionMatch = /Xcode (.*)/.exec(res.stdout)
     if (res.code !== 0 || !versionMatch) {
       console.error('Unable to parse xcodebuild version.')
       return
@@ -52,7 +53,7 @@ const extensions = {
         console.error('Could not get device list.')
         return
       }
-      const listOutput = JSON.parse(res.output)
+      const listOutput = JSON.parse(res.stdout)
       const device = Object.keys(listOutput.devices)
         .reduce(function (acc, key) { return acc.concat(listOutput.devices[key]) }, [])
         .find(function (el) { return el.udid === deviceid })