Add background to memory usage equations

README.md

@@ -144,10 +144,10 @@ When an ordering is not needed, a hash container is typically a better choice th
 
 |  type                 |    memory usage   | additional *peak* memory usage when resizing  |
 |-----------------------|-------------------|-----------------------------------------------|
-| flat tables           | ![flat_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_mem_usage.gif?raw=true) | ![flat_peak_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_peak.gif?raw=true) | 
-| node tables           | ![node_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_mem_usage.gif?raw=true) | ![node_peak_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_peak.gif?raw=true) | 
-| parallel flat tables  | ![flat_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_mem_usage.gif?raw=true) | ![parallel_flat_peak](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/parallel_flat_peak.gif?raw=true) | 
-| parallel node tables  | ![node_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_mem_usage.gif?raw=true) | ![parallel_node_peak](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/parallel_node_peak.gif?raw=true) | 
+| flat tables           | ![flat_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_mem_usage.png?raw=true) | ![flat_peak_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_peak.png?raw=true) |
+| node tables           | ![node_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_mem_usage.png?raw=true) | ![node_peak_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_peak.png?raw=true) |
+| parallel flat tables  | ![flat_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/flat_mem_usage.png?raw=true) | ![parallel_flat_peak](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/parallel_flat_peak.png?raw=true) |
+| parallel node tables  | ![node_mem_usage](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/node_mem_usage.png?raw=true) | ![parallel_node_peak](https://github.com/greg7mdp/parallel-hashmap/blob/master/html/img/parallel_node_peak.png?raw=true) |
 
 
 - *size()* is the number of values in the container, as returned by the size() method