Add nanometers.
Merge pull request #40 from transcriptic/nanometers

Thanks for your contribution
Vector improvements
Merge pull request #41 from garyKeorkunian/wip-127

Vector improvements
Tests for Nanometers and other improvements to Length
Merge pull request #43 from garyKeorkunian/wip-128

Tests for Nanometers and other improvements to Length
Additional Volume units
Merge pull request #44 from garyKeorkunian/wip-volume

Additional Volume units