Expose weekday as integer.

This will allow clients to format and display the weekday name as they
please. The recommended way for a Rails client such as Ohana Web Search
would be to add an entry to the I18n file, such as `en.yml`, that would
look like this:
```
weekdays:
  - Monday
  - Tuesday
  - Wednesday
  - Thursday
  - Friday
  - Saturday
  - Sunday
```
You can then access the weekday String by doing this:
`I18n.t(‘weekdays’)[weekday - 1]`

Closes #273.