Merge pull request #2 from mweastwood/improvements

interface improvements for creating measures and interacting with tables
First piecies of documentation

This is based on the currently defined tests.
Include development note in the readme
Merge pull request #3 from mweastwood/improvements

Improve the q_str macro and add tests for quantity construction
Fix the build process so that the shared library gets an absolute path

Previously, the path of the shared library was specified as a relative
path. This works if you're in the correct directory, but doesn't work in
general.