Add support for XHTML5 pages

Hi,

Version: Glimpse.Core 1.5.0.0 and 1.6.0.0

Glimpse throws multiple js exception when using on a XHTML5 web page (html doctype and application/xhtml+xml as content-type)
The bug is because of attempt to insert incorrect generated js and html in the DOM.

I fixed that on the following commits:
https://github.com/LordVeovis/Glimpse/commit/f19bb8a1b01ce6b71646101ed51b5b7948d5590b
https://github.com/LordVeovis/Glimpse/commit/3a35c0788ab3430dfc267d7e2ff12764f68fc3a0
https://github.com/LordVeovis/Glimpse/commit/d97aa8a9d8f6f5298f9c04ca56ca21854218c8c2

Thanks for the review