Better use of FromError.
Make the reader/writer more configurable.

This adds support for changing quote characters, escaping styles,
quote styles and record terminators.

There should be only one breaking change: the `crlf` method has been
removed from `csv::Writer` and replaced with a more general
`record_terminator` method. Code that used `crlf(true)` to enable
CRLF record terminators can now use
`record_terminator(RecordTerminator::CRLF)` instead. (The default
record terminator remains unchanged at '\n'.)

[breaking-change]
Fix a doctest and explain a particular weird quoting rule.
0.7.0