Add a class to represent myria relation keys
myrial parser returns RelationKeys
Add some type assertions to myrial interpreter
Create RelationKey instances in fakedb ingest
Remove shebang line from interpreter.py
Add hash function to RelationKey
Fix argument names in fakedb
Fix myrial optimizer tests
Use RelationKey for datalog Scan operations
Fix output of raco.tests
Remove redundant relation key functionality from myrialang.py
Use RelationKey in the root Store operation
myrial: add test for multiplicity check

See #87

Signed-off-by: Daniel Halperin <dhalperi@cs.washington.edu>
myrial/parser: fix distinct for SQL syntax

opt_distinct assumed that arg lengths would be different when the token
was empty. Instead, the missing DISTINCT is reflects as a None in that
field rather than the field being missing.

Fix #87

Signed-off-by: Daniel Halperin <dhalperi@cs.washington.edu>
Merge pull request #89 from uwescience/dhalperi-fix-plan-bugs

Dhalperi fix #87
Allow for nesting of SQL expressions
Test of sql nested in bag comprehension
Test SQL nested in SQL
Test bagcomp nested in SQL
fix typo