[Python binding] Add capstone.egg-info to .gitignore

This directory gets created if you install using pip in editable mode.
diff --git a/.gitignore b/.gitignore
index c38e5f8..bbe0c16 100644
--- a/.gitignore
+++ b/.gitignore
@@ -22,6 +22,7 @@
 
 # python
 bindings/python/build/
+bindings/python/capstone.egg-info/
 *.pyc
 
 # java