No need to replace relative paths into absolute paths

Inspired by #5.

I don't remember why I first opted to replace whole paths by their absolute versions, there's no reason I can think of now. Instead of replacing
`var path = '../oops/../images/ajax-loader.gif';`
into
`var path = '/images/ajax-loader.4e26f87c.gif';`
this PR will only replace the filename, so
`var path = '../oops/../images/ajax-loader.4e26f87c.gif';`