In Segment.Split, we didn't take cell width into account
when calculating the offset, which resulted in some "fun" bugs.
I've added a new overload for Segment.Split and obsoleted the old one.
Closes#150
Removed the verbs from all extension methods that manipulate
properties which makes the API more succinct and easier to read.
Also added implicit conversion from string to Style.
As a good OSS citizen, I've obsoleted the old methods with
a warning for now, so this shouldn't break anyone using
the old methods.
