trivial: some small fixes in exofs documentation

Add exofs.txt to filesystems Documentation index and fix some typos,
identation and grammar.

Signed-off-by: Thadeu Lima de Souza Cascardo <cascardo@holoscopio.com>
Signed-off-by: Boaz Harrosh <bharrosh@panasas.com>
diff --git a/Documentation/filesystems/00-INDEX b/Documentation/filesystems/00-INDEX
index f15621e..7001782 100644
--- a/Documentation/filesystems/00-INDEX
+++ b/Documentation/filesystems/00-INDEX
@@ -36,6 +36,8 @@
 	- info about directory notification in Linux.
 ecryptfs.txt
 	- docs on eCryptfs: stacked cryptographic filesystem for Linux.
+exofs.txt
+	- info, usage, mount options, design about EXOFS.
 ext2.txt
 	- info, mount options and specifications for the Ext2 filesystem.
 ext3.txt