tests for different utils (string, map, regex)

[ulitol97]

This PR implementes new test cases to enhance the repo codecov as part of #4
Three commits are included:

75ada2a , new tests for string utils and avoid out of bounds exception (when the string had only one character the functions kept looking for the next character)
d40de22 , new tests for MapUtils to cover more of MapUtils functionality

291a0b6 , new tests for regex to cover more of RegexUtils functionality

The IDE added some "false" insertions/deletions 🙄

[codecov]

Codecov Report

Merging #20 into master will increase coverage by 4.04%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master      #20      +/-   ##
==========================================
+ Coverage   35.82%   39.87%   +4.04%     
==========================================
  Files          23       23              
  Lines         494      494              
  Branches       39       42       +3     
==========================================
+ Hits          177      197      +20     
+ Misses        317      297      -20

Impacted Files	Coverage Δ
.../utils/src/main/scala/es/weso/utils/StrUtils.scala	91.35% <83.33%> (+22.22%)	⬆️
...tils/src/main/scala/es/weso/utils/RegexUtils.scala	100% <0%> (+16.66%)	⬆️
.../utils/src/main/scala/es/weso/utils/MapUtils.scala	100% <0%> (+25%)	⬆️

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[thewillyhuman]

Awesome, thanks!