Support different time intervals

[GuusLieben]

Related Problem

Currently graphs are only created on a per-day basis, causing longer time periods (e.g. 365 days/1 year) to use a large amount of horizontal space. For example:

Requested Feature

Allow users to provide a interval parameter, to allow them to configure the interval. Logical options would be days, weeks, and months. If GitHub's API supports it, hours might also be interesting.

Something to note would be the X-axis labels. Currently these display the day of the month, these should adapt to the interval appropriately (days: as is, weeks: week of year, months: month name?).