Follow the recommendations and use python -m pip instead of pip

See https://snarky.ca/why-you-should-use-python-m-pip/

Author: matthiask

docs/contributing.rst

@@ -32,7 +32,7 @@ you'll have to deactivate it for this repository::
 Once you've obtained a checkout, you should create a virtualenv_ and install
 the libraries required for working on the Debug Toolbar::
 
-    $ pip install -r requirements_dev.txt
+    $ python -m pip install -r requirements_dev.txt
 
 .. _virtualenv: https://virtualenv.pypa.io/
 

docs/installation.rst

@@ -9,7 +9,7 @@ Getting the code
 
 The recommended way to install the Debug Toolbar is via pip_::
 
-    $ pip install django-debug-toolbar
+    $ python -m pip install django-debug-toolbar
 
 If you aren't familiar with pip, you may also obtain a copy of the
 ``debug_toolbar`` directory and add it to your Python path.
@@ -19,7 +19,7 @@ If you aren't familiar with pip, you may also obtain a copy of the
 To test an upcoming release, you can install the in-development version
 instead with the following command::
 
-     $ pip install -e git+https://github.com/jazzband/django-debug-toolbar.git#egg=django-debug-toolbar
+     $ python -m pip install -e git+https://github.com/jazzband/django-debug-toolbar.git#egg=django-debug-toolbar
 
 Prerequisites
 -------------

example/README.rst

@@ -15,7 +15,7 @@ How to
 
 The test project requires a working installation of Django::
 
-    $ pip install Django
+    $ python -m pip install Django
 
 The following commands must be run from the root directory of a checkout of
 the debug toolbar, ie. the directory that contains ``example/``.