Extend the section on testing and fix some spelling errors

CONTRIBUTING

@@ -1,36 +1,40 @@
 How to contribute to *silx*
 ---------------------------
 
-This document describes how to contribute to the *silx* project. 
-The process is similar to many other open-source project like *numpy*, just lighter as the project is smaller, so you won't be surprized with the pipeline.
-*scikit-image* provides a nice tutorial `https://github.com/scikit-image/scikit-image/blob/master/CONTRIBUTING.txt` 
+This document describes how to contribute to the *silx* project.
+The process is similar to many other open-source projects like *numpy*, just lighter as the project is smaller, so you won't be surprised with the pipeline.
+*scikit-image* provides a nice tutorial `https://github.com/scikit-image/scikit-image/blob/master/CONTRIBUTING.txt`.
 
 
-1. Create you GitHub account `https://help.github.com/categories/setup/` 
-   and upload your SSH keys
+1. Create your GitHub account `https://help.github.com/categories/setup/`
+   and upload your SSH keys.
 
-2. Fork the silx project from `https://github.com/silx-kit/silx/`. 
+2. Fork the silx project from `https://github.com/silx-kit/silx/`.
    The button is on the top right of the page.
 
-3. Clone your github version locally on the computer you intent to work on. 
-   **git clone [email protected]/user/silx**
+3. Clone your GitHub version locally on the computer you intend to work on.
+   **git clone [email protected]/user/silx**.
 
-4. Make the silx test pass on your computer, using the **python3 run_tests.py**. 
-   You may install the dependencies defined in *requirement.txt*
+4. Install the dependencies defined in *requirements.txt*.
 
-5. Open an issue in `https://github.com/silx-kit/silx/issues` to inform the 
+5. Make the silx test suite pass on your computer, using the **python3 run_tests.py** or
+   **python3 run_tests.py silx.gui.test.test_qt** if you want to test only a subset of it. 
+   You can use **python /path/to/silx/bootstrap.py script.py** to test your scripts without
+   installing silx, but passing the test suite is required.
+
+6. Open an issue in `https://github.com/silx-kit/silx/issues` to inform the
    maintainer of your intentions.
 
-6. Create a local branch to start working on your issue **git branch my_feature**
+7. Create a local branch to start working on your issue **git branch my_feature**.
 
-7. Code, enjoy, but ensure the new code is tested and does not break 
-   the current test-suite.
+8. Code, enjoy but ensure that the new code is tested and does not break
+   the current test suite.
 
-8. Push your local branch to your github account: **git push origin my_feature**
+9. Push your local branch to your GitHub account: **git push origin my_feature**.
 
-9. Create a pull request (PR) from your feature-branch on github to trigger 
-   the review process. Indicate this PR is related to the issue you opened in 5.
+10. Create a pull request (PR) from your feature branch on GitHub to trigger
+    the review process. Indicate this PR is related to the issue you opened in 6.
 
-10. Discuss with the maintainer who is reviewing your code using the github interface.
+11. Discuss with the maintainer who is reviewing your code using the GitHub interface.
 
-If you encounter any problem or have question on how, you can also ask in the issue page. 
+If you encounter any problems or have any questions you can always ask on the issues page.