Add more tests

[gurpreetsingh00885]

Few more tests have been added. pytest is now used to execute the tests. Tests will be more organized now.

Changes:

• pytest is now used for testing
• .travis.yml was changed accordingly
• tests are now stored in a separate tests folder with descriptive names.

[divyam3897]

@gurpreetsingh00885 working on it?

[divyam3897]

Closing due to inactivity, feel free to open when it's ready.