The previous version of stacktrace-parser 0.1.2 had an line in its package.json file that required Node <= 2.x. That line was removed, so it no longer warns on io.js 3.x or Node 4.x.

Similarly, ws 0.8.0 was published with support for the new V8, so it compiles with io.js 3.x and therefore should work with Node 4.x.

Updated the Travis file as well to run on io.js 3.x.

Test Plan:
```
$ nvm use iojs-v3
Now using io.js v3.1.0 (npm v2.13.3)

$ npm i
<no compiler errors>
```