docs: Fix a few typos

[timgates42]

There are small typos in:

• tests/test_assets.py
• zipline/data/minute_bars.py
• zipline/errors.py
• zipline/finance/controls.py

Fixes:

• Should read constraint rather than contraint.
• Should read slippage rather than slipage.
• Should read identifier rather than identifer.
• Should read considered rather than consdered.

Semi-automated pull request generated by https://github.com/timgates42/meticulous/blob/master/docs/NOTE.md

[andycwang]

@.***邮箱联系我，谢谢！

[andycwang]

@.***邮箱联系我，谢谢！