first pass at usage readme
add mailer documentation
give better param/return descriptions
fix requires
add AbstractMethodError
add start of Mailer
set recipients through defaults hash in mailer
add test for 'default hash' in mailer
use templates for mailer
pull the range values into the email
rearrange instance methods
add Metric#yesterday method
add Metric#last_week
add Metric#days_ago and #weeks_ago
Merge pull request #4 from afeld/readme

@fancyremarker => first pass at readme
include the title and the last week of each metric in the email
add Metric#week_average_this_quarter
free time within a Metric
create Metric#weeks_average method
add fixture data