Draw line in commit view at 72 characters

There's only one header line, but there can be many content lines. So it
makes more sense to show the limit for the content.

Author: andrewschleifer

src/PBGitDefaults.m

@@ -8,7 +8,7 @@
 
 #import "PBGitDefaults.h"
 
-#define kDefaultVerticalLineLength 50
+#define kDefaultVerticalLineLength 72
 #define kCommitMessageViewVerticalLineLength @"PBCommitMessageViewVerticalLineLength"
 #define kEnableGist @"PBEnableGist"
 #define kEnableGravatar @"PBEnableGravatar"