fix documents
remove unoptimized code from str_edit_dist.h
add .gitignore entries
add blocksize utilities
add assertion control
add digest utilities
rename some constants and types
rename ffuzzy_digest member names
add documentation in Doxygen
fix block size parsing to match the documentation
add assertion code
add specialized interface

This commit adds several interfaces specifically for
fast comparison and clustering.
expose FFUZZY_MIN_MATCH instead of ROLLING_WINDOW
release 2.0