text: Title: Add `figsize`, `title_fontsize`, and `text_fontsize` parameter for existing plots.
  Body: As discussed in #11 and pointed out by @frankherfert , plots generated by scikit-plot are quite small on Jupyter notebook. Adding a `figsize`, `title_fontsize`, and `text_fontsize` parameter will let the user adjust the size of the plot based on his/her preferences. 
  
  `figsize` should accept a 2-tuple and be kept at a default value of None and passed to the `plt.subplots` function during figure creation. `title_fontsize` should be kept to default value "large" and `text_fontsize` to default value "medium"