csv serializer
test issuing query
test issuing query; use index instead of column name
modify variable schema, get rid of Option type
removed Option field of variable and edge
Make weight variables work with NULL values
Quote weight variable field
Throw meaninful errors with invalid input variables
factor graph binary format (big endian)
binary format grounding
binary format serialization
Add custom holdout query
Merge branch 'develop' of https://github.com/feiranwang/deepdive into develop
update function name (issueQuery), fix factor type encoding
use short to denote factor function type
use short to denote variable type
fix stream name, add unit test for binary serialization, add test classes
remove csv serializer
fix indentation
add sampler for mac