lheberlie/support transform dest url before save

[lheberlie]

@patrickarlt - for your consideration, this feature request will support modifying the page's metadata such as dest and url before the page is rendered and written to disk.

Thank you,

Lloyd

[coveralls]

Coverage remained the same at 91.041% when pulling 5e47366 on lheberlie:lheberlie/support-transform-dest-url-before-save into ea99518 on patrickarlt:acetate-2.