Trading-calendars

This release includes various maintenance commits/fixes as well as updates to numerous calendars for 2020.

Changes:
- The BVMF close time was updated to reflect a recent change (thanks willianpaixao)
- Compatibility fix for Python 3.8 (thanks pando85)
- Holiday fixes for XASX, XNYS, and XNZE (thanks savvyyabby)
- 2020 holidays for XBKK, XBOM, XBUE, XKAR, XKLS, XKRX (thanks pkim81), XLON, XPHS, XSES, XSHG, XTAI, XTKS, XWBO

This release updates several trading calendars with trading holidays that have recently come to our attention. Holidays were added or amended in the following calendars:

- Ireland (XDUB)
- Singapore (XSES)
- India (XBOM) - thanks swapniljariwala for helping us add an election holiday to this calendar!

This release adds the following new calendars:

- Buenos Aires Stock Exchange (XBUE)
- Indonesia Stock Exchange (XIDX)
- Malaysia Stock Exchange (XKLS)
- Moscow Exchange (XMOS)
- Pakistan Stock Exchange (XKAR)
- Philippine Stock Exchange (XPHS)
- Stock Exchange of Thailand (XBKK)
- Taiwan Stock Exchange Corp. (XTAI)

This release adds the following new calendars:

- Budapest Stock Exchange (XBUD)
- Athens Stock Exchange (ASEX)
- Istanbul Stock Exchange (XIST)
- Johannesburg Stock Exchange (XJSE)

This release updates the Poland calendar which was broken for many of its holidays. It also fixes a bug in which the Lima Stock Exchange open time was off by one.

This release adds the following new calendars:
- Poland Stock Exchange (XWAR) - thanks tymurbaniak!
- Santiago Stock Exchange (XSGO)
- Colombia Stock Exchange (XBOG)
- Mexican Stock Exchange (XMEX)
- Lima Stock Exchange (XLIM)
- Prague Stock Exchange (XPRA)

It also includes various miscellaneous dev and build improvements.