Easier non-DB-dependent example && comments in between

[rounakdatta]

Hi, I wrote a simpler example doing away with all the DB dependencies. Yes, I believe your example is more practical, but maybe a beginner may find mine more useful. Also, I decided to add some print statements around poolboy.erl, example.erl, poolboy_sup.erl in order to help the newbie trace out the call flow and understand the internals of poolboy.

*Please note that the example is your's only. I just added / subtracted statements.