Support for 'cacheBlocks' in TScan #260

The TScan struct from Thrift seems to have a 'cacheBlocks' parameter that is not exposed via HappyBase: https://github.com/apache/hbase/blob/master/hbase-thrift/src/main/resources/org/apache/hadoop/hbase/thrift/Hbase.thrift#L154

Is it feasible add support in HappyBase for this? I'm open to doing this myself via a PR but wanted to check first if there is a chance this gets merged if I do so :-)

Thanks!