imazen/resizer — pull request #110 by GravitasExtra (2014-10-10 15:14:24+00:00)
Title: BugFix: TinyCache CanOperate fails if VirtualCacheFile is null

I have reversed the logic in CanOperate as the HasFileIOPermisions
requires a VirtualCacheFile.

I have also put wrappers around HostingEnvironment to facilitate
testing.

I have added a check for CanProcess eventArgs being null. We get a more
sensible excetion that way.