Release v0.0.3

Adding CHANGELOG.md

Avoid using img.fuzz="xxx%" due to potential bug in rmagick 2.15

As a workaround, use "img.fuzz= options.fuzz * QuantumRange / 100.0
Otherwise see this error message:

Input: demo.mov (00:00:04.29, 5.8M)
Output: 'demo2.gif' (128K)
/var/lib/gems/1.9.1/gems/screengif-0.0.1/lib/screengif.rb:92:in `fuzz=': no implicit conversion to float from string (TypeError)
	from /var/lib/gems/1.9.1/gems/screengif-0.0.1/lib/screengif.rb:92:in `block in start'
	from (eval):2:in `each'
	from (eval):2:in `each'
	from /var/lib/gems/1.9.1/gems/screengif-0.0.1/lib/screengif.rb:83:in `each_with_index'
	from /var/lib/gems/1.9.1/gems/screengif-0.0.1/lib/screengif.rb:83:in `start'
	from /var/lib/gems/1.9.1/gems/screengif-0.0.1/bin/screengif:10:in `<top (required)>'
	from /usr/local/bin/screengif:23:in `load'
	from /usr/local/bin/screengif:23:in `<main>'

README: cask install xquartz instead of x-quartz