Macrofied higher-order functions for method definition.
Tweaked readme.
Retain vector type when negating

Fixes #13
Merge pull request #15 from jayschwa/negation

Retain vector type when negating
Addresses #14. Generalized the mapMethod function to work with binary operators.
Add some core tests for scalar operations
Merge pull request #17 from dronir/master

Add core tests
Generalized scalar type in scalar binary ops.