Document clarification: gitmodules, gitattributes

The SYNOPSIS section of gitattibutes and gitmodule fail to clearly
specify the name of the in tree files used.  This patch brings in the
initial `.' and the fact that the `.gitmodules' file should reside at
the top-level of the working tree.

Signed-off-by: Gustaf Hendeby <hendeby@isy.liu.se>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/gitattributes.txt

@@ -7,7 +7,7 @@ gitattributes - defining attributes per path
 
 SYNOPSIS
 --------
-$GIT_DIR/info/attributes, gitattributes
+$GIT_DIR/info/attributes, .gitattributes
 
 
 DESCRIPTION

Documentation/gitmodules.txt

@@ -7,7 +7,7 @@ gitmodules - defining submodule properties
 
 SYNOPSIS
 --------
-gitmodules
+$GIT_WORK_DIR/.gitmodules
 
 
 DESCRIPTION