title: matplotlib: preventing a few very large (or small) values to affect my contour
body: <p>in plotting the data some times there are a few very large (or very small) numbers which, if not taken care of, will affect the contour in a bad way. a solution is to take out the 10% highest and lowest data out of the contour color grading and considering them as less than and more than. the following figure shows the idea:
  <img src="https://i.stack.imgur.com/VzyjB.png" alt="enter image description here"></p>
  
  <p>the two arrow shapes on the top and the bottom of the bar support this idea. any value above 14 will be shown in white and any value below -2 will be shown in black color. how is it possible in matplotlib?
  How can I define:
  - to put the 5% of highest values and 5% of lowest values in two categories shown in the triangular parts in both ends of the bar? (Should I define it the contour operation or are there other ways?)
  - what if I want to give certain values instead of the percentage? for instance, ask to put any value above 14 on the white triangule and any value below -2 as black areas?</p>
  
  <p>Thank you so much for your help.</p>