error-handling.md

TODO(Martin): Discuss error handling in Haskell. Focus on best practices with clear examples and clear guidelines when to use what. The result of this file should be that beginner in Haskell, after reading it, has a good idea of when to use which error handling technique. Also, discuss error vs exception.

Some possibly useful materials:

• https://wiki.haskell.org/Error_vs._Exception
• https://www.fpcomplete.com/haskell/tutorial/exceptions/
• http://blog.ezyang.com/2011/08/8-ways-to-report-errors-in-haskell-revisited/
• https://www.fpcomplete.com/blog/error-handling-is-hard/