Cleaner API. Better documentation. More support for query params.

LI get methods now take all parameters as named arguments
rather than some through query_params and some directly.
Some code has been removed that is no longer needed because
of this change.

Tests have been updated to use the new get function parameters.

Much more documentation has been added to the README.
And, at the very least, a basic description has been added
to all utility functions. The documentation for the two
primary get methods has been improved.

Other misc. changes made to support the new get functions have
been made.