Add some documentation.
-rw-r--r-- 4 .gitignore
-rw-r--r-- 792 README
-rw-r--r-- 763 Rakefile
drwxr-xr-x - bin
drwxr-xr-x - doc
drwxr-xr-x - ext
drwxr-xr-x - lib
-rw-r--r-- 658 senga.gemspec