added tasmo top level description to the repo

copied 

"Tasmo is a system which enables application development on top of event streams and HBase. It’s functionality is similar to a materialized view in a relational database, where data is maintained at write time in the forms it is needed at read time for display and indexing"

from the readme and added it as the repo header. I feel that all repo headers should have the same product description as the readme as its the first thing people see when they come to the main repo