Get the text for tooltip with $.data (not $.attr)

[keriati]

fix for issue #3477

[fat]

Hey @keriati,

Thanks for opening this pull-request! Unfotunately, it looks like it fails to pass the tests neccessary for submitting to bootstrap. The following tests are currently failing:

• should always include a unit test if changing js files

For a full list of issue filing guidelines, please refer to the bootstrap issue filing guidelines.

thanks!