removed "must install pqueue" from documentation, reformatted docs

Signed-off-by: pjs <pjs@alum.mit.edu>

lib/simplekit.rb

 require 'rubygems'
 require 'pqueue'
 
-# You must install the 'pqueue' gem before using SimpleKit:
-# <ul>
-#     <li>gem install pqueue<br>
-#         or<br>
-#     <li>sudo gem install pqueue&nbsp;&nbsp;&nbsp;&nbsp;# on Unix systems/OS X.
-#</ul>
 # Including SimpleKit gives you methods :run, :model_time, :schedule,
 # and :halt as mixins.  You <b>MUST NOT</b> provide your own implementations
 # of methods with these names in your model.  All but :run are
@@ -31,11 +25,10 @@ module SimpleKit
   # This class provides the computation engine for a discrete event
   # simulation model. It uses RubyGem's PQueue class as the priority
   # queue implementation for the pending events list.
-  # <p>Users must create a model class which
-  # <ul><li>implements an init() method;
-  #     <li>Instantiates a model and invokes
-  #         the run() method to start execution.
-  # </ul>
+  #
+  # Users must create a model class which
+  # 	implements an init() method;
+  #     Instantiates a model and invokes the run() method to start execution.
   class EventScheduler
     attr_reader :model_time, :user_model