remove callback from constructor
added ability to set max db size
tweaked code comment for setMaxDBSize
fixed TPKLayer's class namespace
added getDBSize method
modularized bundleReader
modularized storeTile method
renamed value to pointer
modularized bundeXReader
added indexDBShim (for Safari)
added script link to indexDBShim
delete local tile libraries. Switch to script src
switch to using tile libs from github gh-pages
added setDBWriteable property