Add to_cypher() methods to Expression objects. (#353)
Add to_cypher() methods to Expression objects. (#353)

* Add to_cypher() methods to BasicBlock and Expression objects.

* Make code style more consistent. Add missing abstract method.

* Remove `to_cypher()` methods from BasicBlocks, since that's not how they are emitted.

* Fix Cypher inequality operator.

kensho-technologies/graphql-compiler,kensho-technologies/graphql-compiler