[Easy typo fix] #dropthedot from py.test

[weiji14]

Description of the problem

First-timers 1️⃣ only!! This should be about as simple as it gets. You'll literally be removing just a dot . from py.test in the Testing plots section in CONTRIBUTING.md.

In other words, change:

py.test --mpl-generate-path=baseline pygmt/tests/NAME_OF_TEST_FILE.py

to

pytest --mpl-generate-path=baseline pygmt/tests/NAME_OF_TEST_FILE.py

You can edit the file online on Github here or in your Text Editor or Integrated Development Environment (IDE).

For some background on why we've decided to #dropthedot, see https://stackoverflow.com/questions/39495429/py-test-vs-pytest-command and https://twitter.com/davehunt82/status/756080181085872129. Basically it's because py.test will be go away/be deprecated at some point in the future.

How to get help

You can check out our CONTRIBUTING.md file (that's the file you'll be fixing by the way!) or this website https://firstcontributions.github.io/ on how to make your first contribution. Leave a comment below if you'd like to start working on this and feel free to ask for help! It's actually as much of a learning experience for us (guiding new people) as it will be for you 😄

Stretch goals

There's actually another place in the repository that refers to py.test instead of pytest. Can you find it and fix that too?

[Dovacody]

Hello, I just submitted a pull request that fixed this typo. Thank you for posting something to help us new to all of this!