Add modal toggler and respect current url params when profiling

[Masa331]

Hi there,

thanks for this wonderful gem

this pull requests adds 2 features to it

1. respects current page's url params. Until now page params were discarder(they were ignored when generating url with with :lineprofiler => true
2. adds simple modal toggler. When profiling is active, it adds hide/show toggler next to profiler link in Peek menu. This solves Feature request: close or hide button  #10

happy to update the patch if you don't like something, just let me know

Masa331

[Masa331]

Also added another commit which fixes this issue #18 which is due to code being wrapped in double <pre> tags and so having double padding around it