Describe the bug
The missing value plot gets broken for a small missing values percentage.

To Reproduce

df = pd.DataFrame.from_dict({'col': np.ones(1000)})
df.loc[:2] = np.NaN
klib.missingval_plot(df)

Expected behavior
Appropriate positioning of the text, y axes labels

Screenshots

I have a fix, but I'm not allowed to push my branch. How can I do it?

P.S. awesome library, thanks for the work!