[docs] add some clarifications to CONTRIBUTING.md

* using github for small doc-edit type PRs
* conda/virtualenv activation
* which bit of changelog to update

Author: jcb91

CONTRIBUTING.md

@@ -10,6 +10,8 @@ Here is an example issue of how @benelot did it that worked pretty smoothly: [#1
 
 ## Setup development
 
+For small things like fixing typos in documentation, you can [make edits through GitHub](https://help.github.com/articles/editing-files-in-another-user-s-repository/), which will handle forking and making a pull request (PR) for you. For anything bigger or more complex, you'll probably want to set up a development environment, a quick procedure for which is as folows:
+
 1. __Fork and clone__
    First fork this repo, then clone your fork. In this way you become prepared to make a pull request.
 
@@ -21,6 +23,8 @@ Here is an example issue of how @benelot did it that worked pretty smoothly: [#1
 
 2. __Setup__
 
+   If you're using python in combination with some form of virtual environment (e.g. conda, virtualenv), make sure you have the correct environment (the one from which you run `jupyter notebook`) active before running these commands!
+
    ```shell
    # run from the main directory, where setup.py is
    pip install --editable .
@@ -39,4 +43,4 @@ As you are ready with your code contribution, make a pull-request to the main re
 
 Here is an example pull request of how @benelot did it that worked super well: [#1213](https://github.com/ipython-contrib/jupyter_contrib_nbextensions/pull/1213)
 
-Please also update the [CHANGELOG.md](https://github.com/ipython-contrib/jupyter_contrib_nbextensions/blob/master/CHANGELOG.md).
+Please also update the [unreleased section](https://github.com/ipython-contrib/jupyter_contrib_nbextensions/blob/master/CHANGELOG.md#unreleased-aka-github-master) of the [CHANGELOG.md](https://github.com/ipython-contrib/jupyter_contrib_nbextensions/blob/master/CHANGELOG.md) to note what you've added or fixed.