workday -> working day refs #12
weekend with the "_" refs #12
fixed_holidays instead of fixed_days closes #12
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
Merge pull request #16 from novapost/12-code-nomenclature

code nomenclature fixes