Define an abstract Vector
:)
Implement VectorHash : Vector that is based on HashMap
:)
Use foldMap instead of : _*
Fix sub / add
:)
Turn on scalacheck
Complete test VectorHashScala
Implement unified test for both implementations of Vector
Organize imports
Implement clear* functions
Merge remote-tracking branch 'origin/abstract_vector'

Conflicts:
	README.md