Adding initial README.
Adding initial README.

Signed-off-by: Ben Corlett <9fc0b04505a02c47a9e61f970105683228d674a6@me.com>

BootstrapCMS/Sentry,gazsp/sentry,intrip/sentry,cartalyst/sentry,halfik/sentry,anndro/SentryLdap,jgodish/sentry