Maintenance version

Improvements

• in s2 strings multi-line examples are now possible by aligning text or using a margin

s2"""
  Introduction
    an example
    with 2 lines $ok

    |an example
    | with a very
    |   specific indentation $ok
"""

Fixes

• added a method to allow writing file must not exist #297
• collect NotImplementedErrors in AllExpectations #298
• re-throw exceptions when using the Result.unit method #299

==========================