Increase Coverage

[brodieG]

I looked into increasing coverage and it seems like there is a bit of code that isn't in use, such as:

• data_frame, which I think has been mostly superseded by the switch to matrices that I made a while back
• the code in disposable.r, which as far as I can tell isn't currently in use?

I can submit a PR addressing those plus other low hanging fruit if you're interested. I imagine there is a reason why disposable.r is in the package though.

[gaborcsardi]

disposable.r is actually used, here: https://github.com/gaborcsardi/crayon/blob/e608c57d0785ce3e269bf2c80a4b30ccb489ce3e/tests/testthat/test-styles.r#L14

[brodieG]

Ah, that is the skipped test, makes sense.

[gaborcsardi]

I have increased it a bit. Will do more later.