WIP - #18, #19 - User agent and widths

Renamed screenshot-html to just screenshot and added the start of a preset list.
[#12] - Output directory defaults to current directory.
[#5] - Added a check is webkit2png is available. We might be able to use this to detect other screenshot apps down the road.
Fixed group not getting a single url.

Fixes issue #21
Release 0.1.3
Fixed incorrect base path.

Fixes issue #21
WIP - More options for webkit2png.

Issues #18 #19
Working profiles and mobile view. See readme for usage.

Fixed issue #18 #19
Merge branch 'master' into feature/webkit2png-options

Conflicts:
	History.md
	lib/screenshot.js
	package.json
Merge pull request #25 from firstandthird/feature/webkit2png-options

Adds support for presets, user agents, height&width