Comma or no comma before "too"?

Consider the following examples:

• "And it is a bottle, too."
• "And it is a bottle too."

Is there a semantic difference between these two sentences? Or do they mean the same thing, with or without the comma before "too"? If not, what is the correct usage of the comma in context of "too"?

Solution 1:

According to the Chicago Manual of Style (subscription-based, sorry), you need to use the comma before too "only when you want to emphasize an abrupt change of thought."

Here's an article that gives that quote and has other illuminating things to say on the subject: http://www.dailywritingtips.com/comma-before-too/

Edited to add example from the second link:

He didn’t know at first what hit him, but then, too, he hadn’t ever walked in a field strewn with garden rakes.
In most other cases, commas with this short adverb are unnecessary.