This leads to more consistent formatting across entire Aiken programs.
Before that commit, only long expressions would be formatted on a
newline, causing non-consistent formatting and additional reading
barrier when looking at source code.
Programs also now take more vertical space, which is better for more
friendly diffing in version control systems (especially git).
This however enforces that the argument unifies to a `String`. So this
is more flexible than the previous form, but does fundamentally the
same thing.
Fixes#378.