Updates travis config

Tweaks to docs css

Update README and travix config

Update README.md

Bump up to 0.0.6

Fixes tests, and raise exception with error with command fails

Yabbie should raise in case it gets an error from cmd

Allow slimerjs command to be set so we can use with docker

Move slimerjs executable to be configurable

Extracts width & height for default.js

Bump up to 0.0.5

Updates default.js to initialise page properly as well as to receive the output file.

Bump up yabbie to 0.0.4

Run tests for Ruby 2.1.3

Expands default.js to get absolute url