Added a show_year option for date_range

defaults to true, allows the year to not be shown when both dates are
in the same year
Updated README for show_year option
Made show_year option backward compatible with 0.0.3
Bump version to 0.1.0

minor version bump because the show_year option is backward compatible
even though the templates changed

using the show_year option won’t be available without updating the
templates though
Merge pull request #4 from mbillard/show_year_option

Show year option