Added some fixes and quality tests

[czgdp1807]

References to other Issues or PRs or Relevant literature

Fixes #76
Closes #77

Brief description of what is fixed or changed

• updated AUTHORS
• fixed documentation
• Added tests for presence of tabs

Other comments

[codecov]

Codecov Report

Merging #78 into master will decrease coverage by 0.055%.
The diff coverage is 90%.

@@              Coverage Diff              @@
##            master       #78       +/-   ##
=============================================
- Coverage   97.671%   97.615%   -0.056%     
=============================================
  Files           23        23               
  Lines         1503      1510        +7     
=============================================
+ Hits          1468      1474        +6     
- Misses          35        36        +1

Impacted Files	Coverage Δ
...datastructs/miscellaneous_data_structures/stack.py	90.243% <ø> (ø)	⬆️
pydatastructs/utils/tests/test_code_quality.py	90.384% <90%> (-0.727%)	⬇️