Browser detection by operating system

Close #38.
Node 0.10 spawn error messsage

Node 0.10 changes the way of handling with failed spawns.

Close #43.
Bring iframe to front

With the new logging interface there's less space for the test itself.
Put the iframe above and over the rest of the page reserving only the space for the top bar.

Close #44
1.2.0
Better handling of phantom page.open

page.open is asynchronous and has a callback to know when the page is opened.
Thanks to that it's possible to better control the page opening and provide more clear messages when something fails.
1.2.1
fix Logging with --no-color outputting objects

colors.js hasn't been updated in npm for a long time but it's being
updated on Github.

The issue here was that when logging from Attester with --no-color
passed in command line, it sometimes logged the String object (console.dir
fashion) instead of a logging a string literal (precisely it was fixed by
https://github.com/Marak/colors.js/commit/5ca667df4a9f86f6c202eca5eb1524cd8d2dd331).

Close #48.