Update install instructions

docs/dev/contributing.rst

@@ -37,7 +37,7 @@ Setting up a development environment
 
 To install the dependencies needed for development, you can use pip::
 
-    $ pip install camelot-py[dev]
+    $ pip install "camelot-py[dev]"
 
 Alternatively, you can clone the project repository, and install using pip::
 

docs/user/install.rst

@@ -25,7 +25,7 @@ Using pip
 
 After :ref:`installing the dependencies <install_deps>`, which include `Tkinter`_ and `ghostscript`_, you can simply use pip to install Camelot::
 
-    $ pip install 'camelot-py[cv]'
+    $ pip install "camelot-py[cv]"
 
 .. _Tkinter: https://wiki.python.org/moin/TkInter
 .. _ghostscript: https://www.ghostscript.com