Added Ruby challenges 24, 25, 26, 92, 96

 new file:   Ruby/challenge24.rb - Sum of Integers from File
 new file:   Ruby/challenge25.rb - Odd Numbers
 new file:   Ruby/challenge26.rb - File Size
 new file:   Ruby/challenge92.rb - Penultimate Word
 new file:   Ruby/challenge96.rb - Swap Case