Add dependency installation instructions

Change-Id: Ic5e35f55ff2fa40c1f93d1c8aad57b7ed58f689c
Reviewed-on: http://review.couchbase.org/43226
Reviewed-by: abhinav dangeti <abhinav@couchbase.com>
Tested-by: buildbot <build@couchbase.com>
Tested-by: thomas anderson <thomas.couchbase@gmail.com>
Reviewed-by: thomas anderson <thomas.couchbase@gmail.com>