Use numpy functions

[mcocdawc]

There are a few numpy functions such as numpy.cross which were not available for numba when I wrote the package.
With this PR the corresponding numpy functions are used instead of the custom ones.

Fixes #113

[codecov]

Codecov Report

Attention: Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Project coverage is 0.00%. Comparing base (9165c76) to head (977778d).
Report is 1 commits behind head on master.

Files with missing lines	Patch %	Lines
...ord/_cartesian_coordinates/_cart_transformation.py	0.00%	7 Missing ⚠️
...oord/_internal_coordinates/_zmat_transformation.py	0.00%	2 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff           @@
##           master    #116   +/-   ##
======================================
  Coverage    0.00%   0.00%           
======================================
  Files          29      29           
  Lines        2783    2763   -20     
======================================
+ Misses       2783    2763   -20     

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