new tick_params: please test

It may be bad practice to add functionality this close to 1.0 release, but I couldn't resist. The lack of an easy and interactive way to modify tick and tick label appearance parameters has seemed like a major shortcoming; manipulation of rcParams prior to creation of an Axes is a clumsy workaround. My proposed solution, now in svn 8453, is the tick_params Axes method and pyplot function. To see how it works, try the following in an "ipython -pyplot" session, pausing at each line to see the result:

tick_params(axis='x', colors='r')
tick_params(axis='y', color='pink', labelcolor='b')
tick_params(direction='out', length=6, width=3)
tick_params(labelright='on', labelleft='off', top='off')
tick_params(labelsize='large', pad=6)
tick_params(reset=True, colors='m')