0.7.0:
 * Trace.label/Stream.label can be used to overwrite default labels
 * better support for huge/tiny y-ticks and plots containing multiple traces
 * adding 'equal_scale' option to plot() method
 * Limited localization support and the time axis(es) can be swapped.
 * traces with same id but different processing steps will not be merged
   anymore using the plot() method
 * accept a list of two values for width of beachballs (using Ellipse patch)
