add methods for symmetric real eigen

[araujoms]

Closes #144

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 96.18%. Comparing base (d76e918) to head (1927f88).
Report is 2 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master     #145      +/-   ##
==========================================
+ Coverage   96.10%   96.18%   +0.07%     
==========================================
  Files          11       11              
  Lines        1645     1651       +6     
==========================================
+ Hits         1581     1588       +7     
+ Misses         64       63       -1     

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[andreasnoack]

Thanks for adding these definitions

[araujoms]

My pleasure. Thanks for merging so quickly.