Typo/Bug in heatmapper.py script

[AIqbal94]

Hi,
I recently came across this and thought to open an issue for it, I think in line 379, it should be np.nan instead of np.NAN

https://github.com/deeptools/deepTools/blob/master/deeptools/heatmapper.py#L379

For me changing it to np.nan fixed the error.

[myliu221]

Hi,

I encountered similar issue with error "AttributeError: module 'numpy' has no attribute 'NAN'" after installing deeptools , and solved using the above method. Thanks.

[WardDeb]

Thanks for the report, this is taken up with #1325, and will be released soon.