copy edits for typos

Signed-off-by: Sam Kleinman <samk@10gen.com>
useless "and" word

Signed-off-by: Sam Kleinman <samk@10gen.com>
Update master-slave.txt

Signed-off-by: Sam Kleinman <samk@10gen.com>
repaired curly bracket

There was 1 additional curly bracket end in doc (cosmetic but still)

Signed-off-by: Sam Kleinman <samk@10gen.com>