ENH: plot histogram
DOC: write doc
DOC: example
DOC: docstring
Merge branch 'master' into ENH_plot_histograms

Conflicts:
	doc/user_guide/visualisation.rst
ENH: improve doc docsting
Style corrections.
DOC: small fix
Some typos and style corrections.
Merge branch 'ENH_plot_histograms' of https://github.com/francisco-dlp/hyperspy into ENH_plot_histograms

Conflicts:
	hyperspy/drawing/utils.py
Merge pull request #171 from pburdet/ENH_plot_histograms

Enh plot histograms