return tuples instead of sets. can we sort it now?
remove Xmas (it was doubled)
now we can sort dates to build a nice chronological calendar. refs #9
updated readme to reflect changes closes #9
small typos and docstring fixes
holidays_dates => holidays_set
typo fix
Merge pull request #14 from novapost/tuples-instead-of-sets

Tuples instead of sets loads of changes in the API
Merge branch 'master' into 12-code-nomenclature

Conflicts:
	README.rst
	workalendar/america.py
	workalendar/asia.py
	workalendar/core.py
	workalendar/europe.py
	workalendar/tests/test_core.py