Extend EDA to include bivariate analysis

[shahules786]

mljar EDA contains only a basic analysis on the distribution of each feature, the idea is to extend this to support bivariate analysis.
for example,
EDA.extend_eda(df,target)
will analyze how each variable in data frame df changes with the target variable.

[shahules786]

hey @pplonski
I have made a PR #178

[shahules786]

@pplonski I have made the requested changes.
About choosing the number of features for heatmap (14), I checked some arbitrary values and also took the aesthetics into consideration as too many features in a figure of (10,10) will not look good. What do you think?