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.
Merge pull request #276 from codeforamerica/expose-weekday-as-integer

Expose weekday as integer.