BUG: handle lock=True in open_rasterio and update docs

[snowman2]

• Closes open_rasterio fails when lock=True #273
• Tests added
• Fully documented, including docs/history.rst for all changes and docs/rioxarray.rst for new API

[codecov]

Codecov Report

Merging #274 (b277d21) into master (fa4a935) will not change coverage.
The diff coverage is 100.00%.

@@           Coverage Diff           @@
##           master     #274   +/-   ##
=======================================
  Coverage   93.94%   93.94%           
=======================================
  Files          12       12           
  Lines        1354     1354           
=======================================
  Hits         1272     1272           
  Misses         82       82           

Impacted Files	Coverage Δ
rioxarray/_io.py	87.67% <100.00%> (ø)

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