making some cosmetic improvements to stock_prices.py example
making some cosmetic improvements to stock_prices.py example

tommy-u/chaco,ContinuumIO/chaco,tommy-u/chaco,ContinuumIO/chaco,burnpanck/chaco,ContinuumIO/chaco,burnpanck/chaco,burnpanck/chaco,tommy-u/chaco,ContinuumIO/chaco