MultiCometFade:
1. Similar to comet function but includes functionality to plot multiple comets which have a fading tail.
2. Also includes video capture.
3. Arguments:
a) ax: axes handle on which to plot trajectories
b) steps: number of steps in the trajectory vector to plot at once.
c) numseg: number of segments that tail is divided up in
d) varargin: Trajectory data.
(i) Each 'argin' is made up of 2 rows. The top row is the 'x'
data (could be time), the bottom row is the 'y' data.
(ii) NOTE: The trajectories must be of the same length
(iii) NOTE: For more than 8 trajecties, add rows into color matrix