Remove redundant hasOwnProperty check and update travis testing

[reyawn]

The additional hasOwnProperty check is unneeded:

• Object.prototype.hasOwnProperty checks if a property is found directly on an object (see hasOwnProperty).
• Object.getOwnPropertyNames returns all properties found directly on an object (see getOwnPropertyNames).

This PR removes the unneeded hasOwnProperty check since it is being performed on the output from Object.getOwnPropertyNames.

It also somewhat "modernizes" the travis tests, dropping testing against the archaic 0.6 and 0.8 versions and adding the more likely 0.10 and up stable versions as well as testing against the latest release.