remove old animation examples.

Closes #2027
modified triplot returned value
BUG: quiverkey must set the vector figure attribute
ENH : improve error invalid error message for subplot

Closes #2098

If user passes in a not-three-digit integer, raise `ValueError`
instead of letting the error propagate up from much farther down
the stack
Merge pull request #2782 from efiring/quiverkey_set_figure

BUG: quiverkey must set the vector figure attribute
Merge pull request #2780 from tacaswell/subplot_errormsg

ENH : improve error invalid error message for subplot
Scipy2013 Sprint: Cleaning F/C example

I cleaned the F/C example as suggested in the Scipy 2013 sprint. I had
the help of @leouieda on this.

For more information, please see #2181.
Clean-up line and marker demos
missing mask for scroll event
Merge pull request #2793 from fariza/scroll_event_gtk3

missing mask for scroll event
fix typo in documentation

beyone -> beyond
Merge pull request #2794 from daydreamt/master

fix typo in documentation
ENH: Added remove methods for legends in figure and axes objects
TST: Added tests for remove of legends on figure and axes objects
Merge pull request #2779 from tacaswell/remove_old_ani

Remove old animation examples.
Merge pull request #2788 from tonysyu/mep12-lines-and-markers-demo

MEP12: Clean-up line and marker demos
Merge pull request #2781 from GBillotey/return_triplot

Triplot returns the artist it adds.
BLD: Replaced assert_is import from nose.tools in test_legend as python 2.6 does not support it
STY: pep8 fixes to test_legend.py
Merge pull request #2798 from cimarronm/legend_remove

Added remove methods for legends in figure and axes objects