change some sentences to help understand
change some sentences to help understand

Pip install tempest will install a package from pip source, not from
a dir,so change it to pip install tempest/

Also change some sentences to help understand

Change-Id: I034b3e94fc35db40bd7f7f68ab20cdcbcfddbc37

vedujoshi/tempest,Tesora/tesora-tempest,cisco-openstack/tempest,zsoltdudas/lis-tempest,zsoltdudas/lis-tempest,masayukig/tempest,bigswitch/tempest,vedujoshi/tempest,LIS/lis-tempest,Tesora/tesora-tempest,Juniper/tempest,sebrandon1/tempest,openstack/tempest,masayukig/tempest,sebrandon1/tempest,openstack/tempest,bigswitch/tempest,cisco-openstack/tempest,LIS/lis-tempest,Juniper/tempest