dispatch special cases for x ** 1 and x ** 2

[rsokl]

No description provided.

[codecov-commenter]

Codecov Report

Merging #266 into master will not change coverage.
The diff coverage is 100.00%.

@@            Coverage Diff            @@
##            master      #266   +/-   ##
=========================================
  Coverage   100.00%   100.00%           
=========================================
  Files           66        66           
  Lines         2407      2413    +6     
=========================================
+ Hits          2407      2413    +6     

Impacted Files	Coverage Δ
src/mygrad/tensor_base.py	100.00% <100.00%> (ø)

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[petarmhg]

Since we also have separate operations for Sqrt and Cbrt, do you also want to check for these cases? I'm not actually sure how worthwhile doing so would be, but otherwise this looks good

[rsokl]

True. Although those aren't much more efficient than the pow implementation