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.
Raise an exception when there is a NaN on the open_and_closes dataframe due to incorrect benchmark data
fixing flake8 problems
Merge branch 'master' of https://github.com/quantopian/zipline

* 'master' of https://github.com/quantopian/zipline:
  MAINT: Use more exact boolean checks for pandas structures.
  BUG: Fix typo in requirements file.
  BLD: Add mock to requirements file.
  BLD: Update to latest tornado release.
  BLD: Update to latest Cython release.
  ENH: Add Brazilian calendar for BMF&Bovespa stock market
  ENH: Factor out API methods. Add support for algo scripts.
ENH:Working version of tradingcalendar as a class
ENH: Adding Trading Calendar as a class specific to trading environment