Update references
Simplify StringCounter::calc_avg()
Consider the leftmost and rightmost boundary
Move string scoring functionality from Segmenter to StringCounter
Move data member `lrv_exp` to StringCounter
Correct StringCounter::calc_avg()
Use std::vector<T>
typedef Index
Merge branch 'develop'
Follow STL naming convention
Add class encoded_multistring
Use encoded_multistring to manage input strings
Remove some unused methods
Refine segmenter::fit_and_segment()
Simpify segmenter::fit_and_segment()