Add support for nested directories.

[dannyvankooten]

Right now, when passing a glob like templates/**/*.tmpl the template name will be assigned using the base of the file. This leaves room for potential issues where several subdirectories have files with the same name though.

When a template is in a subdirectory, the directory name should be included in the template name.

[dannyvankooten]

For those coming across this issue: this is fixed in dannyvankooten/extemplate, which I recommend using instead of Grender.