Trading-calendars

Calendars for the following exchanges were added:

- Bombay Stock Exchange (XBOM)
- Singapore Exchange (XSES)
- Shanghai Stock Exchange (XSHG)

This release includes minor changes regarding the Brazil calendar.

This release adds updates and tests to the Brazil calendar.

Calendars for the following exchanges were added:

- Copenhagen Stock Exchange (XCSE)
- Helsinki Stock Exchange (XHEL)
- Stockholm Stock Exchange (XSTO)
- Oslo Stock Exchange (XOSL)
- Irish Stock Exchange (XDUB)

This release fixes an issue introduced in version 1.3.0 where calendar initialization would fail on Python 3.6 when using pandas 0.18.1.

We have added utilities for computing the dates of holidays based on lunar or solar events. These live in `etc/lunisolar`.

Calendars for the following exchanges were also added:
- Austrialian Securities Exchange (XASX)
- Bolsa de Madrid (XMAD)
- Borsa Italiana (XMIL)
- New Zealand Exchange (XNZE)
- Wiener Borse (XWBO)
- Hong Kong Stock Exchange (XHKG)