Fix minor bug in URI/path comparison.
Fix minor bug in URI/path comparison.

If `uri` is `/subdir/` and the `item.url` is `/subdir/index.html` then
`index.html` needs to be added to `uri` and not `item.url`.

jnordberg/wintersmith,1upon0/wintersmith,jmptrader/wintersmith,MorJar/wintersmith,pridemusvaire/wintersmith,taras/embersmith,pridemusvaire/wintersmith,mimiflynn/wintersmith,MorJar/wintersmith,mimiflynn/wintersmith,jmptrader/wintersmith,cwhatley/wintersmith