Updated README for new configuration

Since plugins are configured in a separate file, the README now tells
people to put commands in plugins.json instead of options.json.

README.rst

 Usage
 -----
 
-1. Copy options.json.tmp to ~/.config/kaylee/options.json and fill the
+1. Copy options.json.tmp to ~/.config/kaylee/options.json.  Default
+   values for command-line arguments may be specified in this file.
+2. Copy plugins.json.tmp to ~/.config/kaylee/plugins.json and fill the
    ".shell" section of the file with sentences to speak and commands
    to run.
-2. Run Kaylee with ``./kaylee.py``. This generates a language model and
+3. Run Kaylee with ``./kaylee.py``. This generates a language model and
    dictionary using the `Sphinx Knowledge Base Tool
    <http://www.speech.cs.cmu.edu/tools/lmtool.html>`__, then listens for
    commands with the system default microphone.
 
 3. Start talking!
 
-**Note:** default values for command-line arguments may be specified in
-the options.json file.
-
 Examples
 ~~~~~~~~
 
 -  To run a command when a valid sentence has been detected:
    ``./kaylee.py --valid-sentence-command=/path/to/command``
 
--  To run a command when a invalid sentence has been detected:
+-  To run a command when an invalid sentence has been detected:
    ``./kaylee.py --invalid-sentence-command=/path/to/command``
 
 Finding the Device Number of a USB microphone