Fix #132 - Add Chrome Headless detection

[chiefcll]

Add Chrome Headless support as Chrome browser to keep it simple
for others to see as Chrome per Issue #127.

[jdalton]

Thank you @chiefcll!

[chiefcll]

Thank you! - This is becoming more important with Chrome Headless playing a much larger role in CI systems.

[bnjmnt4n]

Thanks for the PR! I've only recently gotten back into open source, and will be looking at these commits later this week. What do you think about marking Chrome Headless differently from Chrome though? Should there be a platform.headless option in v2 for Chrome Headless, Phantomjs, and others? Looking for any opinions!

[chiefcll]

I originally had the platform.name as 'Chrome Headless' but then changed it to Chrome due to seeing issue #127 - It might be better to have a platform.type which would then be mobile or headless. I'm not sure how many differences there are between Chrome + Headless + mobile as far as rendering and JS engine.

[omnibs]

Is any missing work preventing this from getting merged? I'd be happy to help.

[omnibs]

ps: I'd like to voice a preference to ferrying this forward and opening a follow-up.

I think misidentifying HeadlessChrome current as Safari 7 is more painful than not differentiating HeadlessChrome from Chrome properly.

[kevinpthorne]

bumping

[bnjmnt4n]

Hi all, sorry for the delay, working on merging some of the open PRs and releasing a new version soon. No firm promises, but expect a new version by the end of next week.