Improve book.findFile to be case incensitive

lib/book.js

@@ -614,12 +614,13 @@ Book.prototype.findFile = function(filename) {
 
             var filepath = basename+ext;
 
-            return that.fileExists(filepath)
-            .then(function(exists) {
-                if (!exists) return null;
+            return fs.findFile(that.root, filepath)
+            .then(function(realFilepath) {
+                if (!realFilepath) return null;
+
                 return {
                     parser: parsers.get(ext),
-                    path: filepath
+                    path: realFilepath
                 };
             });
         });

lib/utils/fs.js

@@ -30,6 +30,7 @@ var fsUtils = {
         fs.exists(path, d.resolve);
         return d.promise;
     },
+    findFile: findFile,
     existsSync: fs.existsSync.bind(fs),
     readFileSync: fs.readFileSync.bind(fs),
     clean: cleanFolder,
@@ -178,4 +179,15 @@ function cleanFolder(root) {
     });
 }
 
+// Find a file in a folder (case incensitive)
+// Return the real filename
+function findFile(root, filename) {
+    return Q.nfcall(fs.readdir, root)
+    .then(function(files) {
+        return _.find(files, function(file) {
+            return (file.toLowerCase() == filename.toLowerCase());
+        });
+    });
+}
+
 module.exports = fsUtils;