Add typical methods for ordered factors and integers

[jrnold]

Add typical methods for integer and ordered factor vectors.

• integer: preserves the integer type instead of returning numeric
• ordered factor: returns the level of the 50% quantile instead of the most frequent.

[hadley]

Can you please add a bullet to NEWS? It should briefly describe the change (starting with name of the function), and crediting yourself with (@yourname, #issuenumber).

[jrnold]

I updated news. I bumped the package version to a dev version 0.1.1.9000

[hadley]

Let me fix the version number (done).

I think something went wrong with your rebase 😞

[jrnold]

Next best thing to burning it all down ... squashed the rebase until it worked.

[hadley]

Thanks!