Exclude directory paths from file system search (#401)

* Exclude directories from file system search

Directories can also match the glob search pattern if their names end in ".php", which will cause a read error later since the ContentRetriever implementers are expecting files. As far as I know, the only way to fix this is to do an additional check to ensure the URI is not of a directory.

This resolves #306.

src/FilesFinder/FileSystemFilesFinder.php

@@ -22,7 +22,11 @@ class FileSystemFilesFinder implements FilesFinder
         return coroutine(function () use ($glob) {
             $uris = [];
             foreach (new GlobIterator($glob) as $path) {
+                // Exclude any directories that also match the glob pattern
+                if (!is_dir($path)) {
                     $uris[] = pathToUri($path);
+                }
+
                 yield timeout();
             }
             return $uris;