Use System.nanoTime() for timeout calculation

This fixes #150.
initial commit for cql based impl for some reads/writes and ddl ops
1. Adding more functionality to describe schema/keyspaces
2. Adding support for async operations
Adding in support for using KeyspaceTracerFactory
Adding keyspace specific tracers
allow fat jar creation
1. Adding support for plugging in cal based driver under AstyanaxContext.
2. Adding unit tests for writes and reads and fixing bugs
Adding unit tests for row slice queries and fixing bugs. Also adding initial support for composite cols.
More code and tests for column range queries and row range queries
Adding capability to switch drivers for testing Astyanax client interface
Cleaning up ColumnQueryTests - which takes care of different kinds of Column Slice queries
Cleaning up ColumnCountQueryTests - this includes tests for column count queries with single rows and also multiple rows
Adding row slice and row range query tests - added option for ALLOW FILTERING
Adding tests for column counts with row range queries - with allow filtering enabled
Adding pagination tests for long columns
Adding in support for composite columns - reads and writes
Adding support for running pert tests. Also adding logic for schema def based ops.
Adding in more functionality for MutationBatch and other smaller fixes
Minor updates only
Adding schema tests and fixing bugs in ddl operations