Update pycmap_histogram.rst

[MSchatzUW]

Megan's edits and comments

[MSchatzUW]

Removed Comments below:

“Creates a histogram graph for each variable according to the specified space-time constraints (dt1, dt2, lat1, lat2, lon1, lon2, depth1, depth2). Change the APIs vizEngine_ parameter if you wish to use a different visualization library.”
..COMMENT: Are you sure the hyperlink above is directing the user to the right page? Doesn't make sense to me why it's directing me to where it is. Do you want it directing the user to the 'API' method page?

“ exportDataFlag: boolean, default: False
If True, the graph data points are stored on the local machine. The export path and file format are set by the APIs parameters_.”
..COMMENT: Are you sure the hyperlink above is directing the user to the right page? Doesn't make sense to me why it's directing me to where it is. Do you want it directing the user to the 'API' method page?

Example
..COMMENT: Maybe I commented on this before but I would add example plots showing what the lines of code are doing to change the plots