provide extension method for flattening partialresults
add tests for new extension method
breaking: make Task<IEnumerable<T>> the Async query return type

 * Partial results are now returned by a method 'AsyncPartial'
 * The default async call will fetch all results for the query
add integration tests for async queries
Merge pull request #86 from jkling/PartialResultFlattening

Add extension method for flattening async partial results lists
Create 8.0.0 release