Om 0.8+ (React 0.12+) compatibility

Fixes #61 

*   Correctly identify React components as not being JS object props
    React components are now plain objects, so (object? x) was including them
    thinking they were something like, #js {:class ""}
*   Adhere to the new pre/post component? conditions. Specifically, mirror this
    fix: swannodette/om@8aa96e2
*   Also added this project to Travis CI to test both om 0.7.X and 0.8.Y