Corpus Christi is a working day in France (fix and unit test included).
Defaulting Corpus Christi to False in the core.ChristianMixing Calendar as it's not a day off for EVERY christian-related calendar, refs #86
Merge pull request #88 from AndreMiras/corpus_christi_is_working_day_in_france

Corpus christi is working day in france
no need to "unflag" the Corpus Christi in the USA
since it's False by default, no need to test it this way
added tests to prevent a True flag in the core module for Christian holidays (there are a lot of them)
making sure there are only 2 holidays by default for a ChristianMixin calendar
Merge pull request #89 from novapost/bugfix-corpus-christi

Bugfix corpus christi -- closes #86 / thx @AndreMiras for the heads up