As if St. Louis'public library systems weren't already the bomb, they've now got an even sweeter offering for patrons: free WiFi hotspots.The St. Louis County and St. Louis city systems have purchased 30 of the devices, the Post-Dispatch reports, and they'll be making them available to patrons for take-home use. Beginning Friday, you can check out the device just like you would a book — and then, using any WiFi enabled device of your own (smartphone, tablet, laptop), connect to the Internet for unlimited free browsing.…