Replace 'pip' with 'python -m pip install' in docs

docs/guide/installing.rst

@@ -12,7 +12,7 @@ MongoEngine is available on PyPI, so you can use :program:`pip`:
 
 .. code-block:: console
 
-    $ pip install mongoengine
+    $ python -m pip install mongoengine
 
 Alternatively, if you don't have setuptools installed, `download it from PyPi
 <http://pypi.python.org/pypi/mongoengine/>`_ and run

docs/index.rst

@@ -7,7 +7,7 @@ MongoDB. To install it, simply run
 
 .. code-block:: console
 
-    $ pip install -U mongoengine
+    $ python -m pip install -U mongoengine
 
 :doc:`tutorial`
   A quick tutorial building a tumblelog to get you up and running with

docs/tutorial.rst

@@ -18,7 +18,7 @@ location --- running it locally will be easier, but if that is not an option
 then it may be run on a remote server. If you haven't installed MongoEngine,
 simply use pip to install it like so::
 
-    $ pip install mongoengine
+    $ python -m pip install mongoengine
 
 Before we can start using MongoEngine, we need to tell it how to connect to our
 instance of :program:`mongod`. For this we use the :func:`~mongoengine.connect`

docs/upgrade.rst

@@ -85,10 +85,10 @@ by default from now on.
 
 The 0.8.7 package on pypi was corrupted.  If upgrading from 0.8.7 to 0.9.0 please follow: ::
 
-    pip uninstall pymongo
-    pip uninstall mongoengine
-    pip install pymongo==2.8
-    pip install mongoengine
+    python -m pip uninstall pymongo
+    python -m pip uninstall mongoengine
+    python -m pip install pymongo==2.8
+    python -m pip install mongoengine
 
 0.8.7
 *****