Fix bug #11

Gnome Books doesn't honour the page/chapter read count and instead re-opens the ebook on the first page (bug #11 (closed)). This is because the value of a slider defaults to the bottom of its range, and the range of the slider defaults to having a min of 0.

Setting an initial range of 1 to 1 gives a valid default value for books and stops the value-changed event triggering when the book's real range is set (because setting 1…N for an N page/chapter book changes a 0…X slider's value to 1, which gets treated as a page change, which overwrites the last page location before the user sees the book)