Merge pull request #12 from fayland/master

call before _build_pk_filter since $delete_ref will be empty afterwards
for count on scan
Support for binary/binary set puts.
Support for reads of binary and binary set.
Support for batch_get of binary fields.
Move handling of sets into _build_value method.
Binary field support in batch_write_item.

Use _build_value method in batch_write_item.
Create test for batch_write_item.
Test with derive_table.
Comments and documentation.
Support Binary in updates.
Merge branch 'master' of git://github.com/ukautz/Net-Amazon-DynamoDB
merge from master