Backus deprecation warning

[mycarta]

Hi Matt

I was playing with your moving_average function in Backus.

I get this warning:

C:***AppData\Local\Continuum\Anaconda2\lib\site-packages\ipykernel__main__.py:9: DeprecationWarning: using a non-integer number instead of an integer will result in an error in the future

Here's what I am trying to average:

[86.544132822954765, 86.204349283696786, 84.263685498914469, 83.619860049308514, 83.415599316141169, 82.512319865929754, 82.812371366274434, 81.430738171894291, 81.027111369532435, 80.768922397914935, 79.657359574573206, 78.978330807691705, 77.421470161724429, 77.125328486430334, 76.51645503846477, 76.245894367769893, 75.082916798472681, 75.09821675713394, 74.812804540979585, 74.197337409857582, 73.933643720603627, 73.655345392427208, 72.797818855466801, 72.81736273625296, 72.259671462235261]