Add minitest spec for ej1.
Add minitest spec for ej2.
Add minitest spec for ej3
Add minitest spec for ej4.
Add minitest spec for ej5.
Add minitest spec for ej6.
Add minitest spec for ej7.
Merge pull request #1 from gramos/add-minitest-specs

Add minitest specs
Update ej5_max_sum.rb
Agrego el ejercicio de la escalera.
Add specs.