Added a struct for storing the bit string
Added the alphabet to the bit string struct
Modified coding and decoding of strings to use the new bit_string struct
Bugfixing in coding and decoding of strings, and introduction of the new
bit_string struct
Added some parameter checking
Added reinitialization of mask in mapping bit string to string
Finished tests for string mapping
Moved print_bits() to utils and added some documentation to it
Moved print_bits() to utils.c
Added some documentation