Updated readme file

Author: AlexMartin17

README.md

@@ -2,7 +2,7 @@
 
 ASCII diff tool written in Python 3 using PyQt<br>
 
-pip install pyqt5<br>
+pip3 install pyqt5<br>
 
 <img src="https://raw.githubusercontent.com/AlexMartin17/amdiff-ascii-diff-tool/master/img/mainui.JPG">
 <img src="https://raw.githubusercontent.com/AlexMartin17/amdiff-ascii-diff-tool/master/img/files.JPG">