PyModel/README.md, tweak formating, clarify prerequisites

Author: jon-jacky

README.md

@@ -28,20 +28,20 @@ programmed *strategies*.
 
 PyModel provides three main programs:
 
-- *pma*, PyModel analyzer: generates a finite state machine (FSM) 
+- **pma**, PyModel analyzer: generates a finite state machine (FSM) 
    and computes properties by exploring a model program, FSM, test suite, 
    or a product of these.  Optionally checks safety properties.
 
-- *pmg*, PyModel graphics: generates a file of graphic commands from an FSM,
+- **pmg**, PyModel graphics: generates a file of graphic commands from an FSM,
    that can be processed by the Graphviz *dot* command to produce graphics
    files in various formats including *svg*, *pdf*, and *ps*.
 
-- *pmt*, PyModel tester: displays traces, generates tests offline, 
+- **pmt**, PyModel tester: displays traces, generates tests offline, 
    executes offline tests, or generates and executes tests on-the-fly.
 
 There is also a fourth program:
 
-- *pmv*, PyModel viewer: invokes *pma*, *pmg*, and the Graphiz *dot* command
+- **pmv**, PyModel viewer: invokes *pma*, *pmg*, and the Graphiz *dot* command
    (to display the graphics generated by *pmg*).  The *pmv* program
    provides brevity and convenience, so analysis and display can be
    accomplished by a single command.
@@ -53,7 +53,7 @@ For more information, read the [notes](notes), peruse the
 PyModel is also available at
 [PyPI](http://pypi.python.org/pypi/PyModel).
 
-PyModel requires Python 2.6 (because it uses *itertools.product*)
+PyModel requires Python 2.6 or higher (because it uses *itertools.product*)
 
 PyModel is influenced by [NModel](http://www.codeplex.com/NModel), but
 is not a translation or re-implementation.