Add NSFileManager entry

Foundation.md

@@ -1,3 +1,24 @@
 # Foundation
 
+- [NSFileManager](#nsfilemanager)
+
 ---
+
+### NSFileManager
+
+#####- (NSDictionary *)attributesOfItemAtPath:(NSString *)filePath error:(NSError *)error
+
+When attempting to retrieve an attribute of a file on disk, using `–[NSFileManager attributesOfItemAtPath:error:]` will expend an excessive amount of time fetching additional attributes of the file that you may not need. Instead of using `NSFileManager`, you can directly query the file properties using `stat`:
+
+```objective-c
+//#import <sys/stat.h>
+
+struct stat statbuf;
+const char *cpath = [filePath fileSystemRepresentation];
+if (cpath && stat(cpath, &statbuf) == 0) {
+    NSNumber *fileSize = [NSNumber numberWithUnsignedLongLong:statbuf.st_size];
+    NSDate *modificationDate = [NSDate dateWithTimeIntervalSince1970:statbuf.st_mtime];
+    NSDate *creationDate = [NSDate dateWithTimeIntervalSince1970:statbuf.st_ctime];
+    // etc
+}
+```

README.md

@@ -7,9 +7,10 @@ Most code substitutions documented here consist of replacing high-level APIs tha
 ### Table of Contents
 
 **iOS App Performance Cheatsheet** is sectioned into Markdown files by Objective-C framework:
-- [Foundation](Foundation.md)
-- [UIKit](UIKit.md)
-- [QuartzCore](QuartzCore.md)
+- [**Foundation**](Foundation.md)
+	- [NSFileManager](Foundation.md#nsfilemanager)
+- [**UIKit**](UIKit.md)
+- [**QuartzCore**](QuartzCore.md)
 
 ### Why is this on GitHub?