1.2.0

• This feature is NEW and EXPERIMENTAL.
  Implemented support for multiple values inside in a sequence.
  This will allow the defenition of different types that one sequence can contain. You can either require
  each value in the sequence to be valid against one to all of the different possibilities.
  Tests show that it still maintains backward compatibility with all old schemas but it can't be guarantee.
  If you find a regression in this release please file a bug report so it can be fixed ASAP.
• This feature is NEW and EXPERIMENTAL.
  Added ability to define python files that can be used to have custom python code/functions that can be
  called on all types so that custom/extra validation can be done on all data structures.
• Add new keyword 'func' that is a string and is used to point to a function loaded via the extension system.
• Add new keyword 'extensions' that can only be used on the top level of the schema. It is should be a list
  with strings of files that should be loaded by the extension system. Paths can be relative or absolute.
• New cli option '-e FILE' or '--extension FILE' that can be used to load extension files from cli.
• Fixed a bug where types did not raise exceptions properly. If schema said it should be a map but data was
  a sequence, no validation error was raised in earlier versions but now it raises a 'NotSequenceError' or
  'NotMappingError'.