Add unit tests

[daniellimws]

Features that need tests (update list when done):

• Searching
• Pop pop ret
• Update badbytes
• Commenting
• Add custom line
• Merging
• Splitting
• Exporting
• Saving
• Loading

[daniellimws]

http://johnnado.com/pyqt-qtest-example/
https://wiki.python.org/moin/PyQt/GUI_Testing

[daniellimws]

a787597