Add a width option per time signature
This width option is used so that we can figure out whether the
thumbnail will fall off the player or not.
Also, move setting 'left' to after we get the mouseTime so we get the
proper mouseTime setting.
Use settings[mouseTime].width for visible width
If the above option is available, use that. Otherwise, try and get it
from the initial setting: settings[0].
Also, rename 'getWidth' to 'getVisibleWidth'.