[Test] Added tests for queue #61

[shivsubh]

Added unit tests for the pyqueue in tests/queue_tests.py

changes done:

• [x] write tests for pyqueue in tests/.
• [x] updated the pyqueue in dsalgo.
• [x] updated the queue branch with the master.
• [x] pull request for queue branch.

closes #61

[shivsubh]

@codesankalp please review this pull request