csvlook should support string values with new lines

[dylan-chong]

The following is a valid csv file

a,b,c
A,"this is
a multi
line
b", C

but csv look prints this as

| a | b                      | c  |
| - | ---------------------- | -- |
| A | this is
a multi
line
b |  C |

csvlook should have multiline cells, or (the easier way) escape new lines by displaying them as \n

[jpmckinney]

Upstream issue wireservice/agate#749 and PR wireservice/agate#750

There's a question in the issue that I need feedback on.