Typedargs

- Provide more helpful error messages when an external module cannot be
properly imported. Now we log the exception using the logging module.

- Move pyreadline to a windows only dependency as it should be.

- Add support for passing complex lists on the command line and converting from
string to list using ast.literal_eval to safely evaluate the string
expression.
- Add experimental ParsedDocstring class to help generalize the docstring
parsing used in docannotate.
- Add experimental terminal size querying routines to support better help string
printing in the shell.
- Add additional functionality to metadata

- Fix valid_identifiers() on python 3 that was adding dict.keys() which is no
longer supported.
- Fix negative numbers being misinterpreted as flags.
- Fix equals signs in --flag=name=value causing an exception due to incorrect
splitting logic.

- Fix issue with bytes type that did not properly allow specifying hex strings
during the conversion to being python 3 compliant. (Issue 25)

- Add support for indicating contexts and stringable return values in
docannotate. (Issue 22)