Update changelog for 0.3 release

Mark date 0.2 release was created. Perpare changelog items for comming
0.3 release.
Add basic usage examples to examples collection

Create a new subdirectory below the package documentation to hold the
existing examples as well as add the existing examples already used in
the package README file.
Use argparse internally for command line parsing

Replaces the internal use of optparse in favour of using argparse for
command line parsing.