Add colorpicker gemfile and import assets

Signed-off-by: Pedro Paulo <pedro@vezza.com.br>
Add colorpicker to Reading View

signed-off-by: Thiago Kenji Okada <thiago.mast3r@gmail.com>
signed-off-by: Fellipe Souto <fllsouto@gmail.com>
Fixed colorpicker's Javascript to automatically get ID

signed-off-by: Thiago Kenji Okada <thiago.mast3r@gmail.com>
Fix indentation and cleaned code
Change colorpicker to use a input button instead of image

Visually is much better and less hacky