CssRewriteUrlTransform doesn't account for virtual paths

When processing CSS files in a bundle, the CssRewriteUrlTransform class
doesn't account for virtual paths, instead assuming that the application
is located at the domain root (assumes http://foobar.com/, but it's
actually http://foobar.com/Git).  This change implements a new wrapper
class that ensures that virtual directories are taken into account.

Since it just modifies the path and then passes it to the original
class, this should be low risk.  If the bug is ever fixed in the
framework there will be a regression, but the bug will leave users no
worse off than they are now.

Found solution from http://aspnetoptimization.codeplex.com/workitem/83
via
http://stackoverflow.com/questions/19765238/cssrewriteurltransform-with-or-without-virtual-directory

Tested the change using IIS Express on my local machine (no virtual path
required) and on my production IIS server (using a virtual path).  Both
tests were successful.
Merge branch 'master' of https://github.com/doggy8088/Bonobo-Git-Server
Merge pull request #100 from kfarnung/master

CssRewriteUrlTransform doesn't account for virtual paths
Merge pull request #101 from doggy8088/master

zh-TW (Traditional Chinese) translation added
Merge branch 'master' of github.com:jakubgarfield/Bonobo-Git-Server
Languages ordered
Prepare for release 3.1.
Fix #102 Removed if causing the create team button dissapear
Changelog updated
Small speed improvement for larger repositories
Last commit from ancestors algorithm optimization
Fixed #104 Missing highlight.pack.js
Loading repository details asynchronously
Date string added to model for better JSON cooperation
BrowseTree refactoring
Ignore Microsoft Roslyn
Resource satellite assemblies do not use code generator
Replace ContentDispositionUtil with official version and correct license
Expose all cultures available in a cleaner and more friendly format
Merge pull request #113 from Duikmeester/master

Expanded functionality for resources