Fix linked files rendering:
Fix linked files rendering:

* Fix bug where providing a filename on the commandline fails
* Resolve subdirectories with the default files, e.g. README.md

jbarreras/grip,ssundarraj/grip,joeyespo/grip,ssundarraj/grip,mgoddard-pivotal/grip,mgoddard-pivotal/grip,jbarreras/grip,joeyespo/grip