Fix readme spelling

Author: taylormonacelli

README.rst

@@ -37,7 +37,7 @@ Are you studying binary trees for your next exam, assignment or technical interv
 
 **Binarytree** is a Python library which provides a simple API to generate,
 visualize, inspect and manipulate binary trees. It allows you to skip the
-tedious work of setting up test data, and dive straight into practising your
+tedious work of setting up test data, and dive straight into practicing your
 algorithms. Heaps and BSTs (binary search trees) are also supported.
 
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