Apply file transforms before processing them

Fixes the case where you ask for a transform when bundling your files
(CssRewriteUrlTransform, for example, as in "new
LessBundle("~/bundles/css").Include("~/Content/site.less", new
CssRewriteUrlTransform())") : the previous code reads the file from
disk, omitting to apply the transforms. This is now fixed.
Merge pull request #7 from nop00/master

Apply file transforms before processing them