Make a local patched version of plot_cxctime

Upgrading matplotlib from 1.1 to 1.2 introduced a change
in the fig.canvas attribute which breaks esaview.  This
update makes a patched version of plot_cxctime that doesn't
call fig.canvas.draw().
Merge pull request #2 from sot/matplotlib-fix

Make a local patched version of plot_cxctime