Documentation: merge: move merge strategy list to end

Documentation: merge: move merge strategy list to end

So the section layout changes as follows:

 NAME
 SYNOPSIS
 DESCRIPTION
 OPTIONS
-MERGE STRATEGIES
 HOW MERGE WORKS
 HOW CONFLICTS ARE PRESENTED
 HOW TO RESOLVE CONFLICTS
 EXAMPLES
+MERGE STRATEGIES
 CONFIGURATION
 SEE ALSO
 AUTHOR
 DOCUMENTATION
 GIT
 NOTES

The first-time user will care more about conflicts than about
strategies other than 'recursive'.

One of the examples uses -s ours, but I do not think this hinders
readability.

Suggested-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Thomas Rast <trast@student.ethz.ch>