Add installation guide
Don't instantiate HighLine when not tty
Add EPUB::Search::Database class
Add Database#db_file method
Remove Init::FILE_NAME constant
Move setting of Groonga from action to initialize
Don't call Pathname.new when already a Pathname
Move logic of adding to lib
Move logic of remove to lib
Extract access to table to a method
Extract Groonga::Database.open to a method
Move search code to lib
Move setting variable up out of Groonga block
Modify slightly
Remove unused variable
Move search logic to from app to lib
Fit watch to new APIs
Use library APIs on watching
Stop caching Page table access

It causes core-dump to access Page table after closing Groonga database.
Add overwrite switch to add command