added Brazilian calendar for BMF&Bovespa stock market
Added Brazilian Bovespa Stock Market calendar
Merge branch 'master' of https://github.com/quantopian/zipline

* 'master' of https://github.com/quantopian/zipline:
  BUG: Make itervalues in empty position test Python 3 compatible.
  ENH: Filter out empty positions from portfolio container.
  ENH: Always process new orders
  MAINT: Updated requests requirement to 2.2.0
  MAINT: Use date range in example that that has 1 Month curves.
  DOC: Fix link to flake8 homepage.