RF: Add rev_run as shim for core's run

[kyleam]

core's run has been the same as rev_run since eba3ccfd6 (BF: run: Save
results with rev-save, 2019-03-18). As of datalad/datalad#3409, core
is dropping its rev_run shim, so add it here.

[codecov]

Codecov Report

Merging #128 into master will increase coverage by 1.17%.
The diff coverage is 87.5%.

@@            Coverage Diff             @@
##           master     #128      +/-   ##
==========================================
+ Coverage    77.5%   78.67%   +1.17%     
==========================================
  Files          10       11       +1     
  Lines         120      136      +16     
==========================================
+ Hits           93      107      +14     
- Misses         27       29       +2

Impacted Files	Coverage Δ
datalad_revolution/__init__.py	100% <ø> (ø)	⬆️
datalad_revolution/revrun.py	87.5% <87.5%> (ø)

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