Added step to populate data with sql file, preventing error

Was getting the following error on the postinstall script:

foo@bar:~/formhandler-example-fork$ perl postinstall
DBD::SQLite::db selectrow_array failed: no such table: book at postinstall line 16.
DBD::SQLite::db prepare failed: no such table: book at postinstall line 19.
Can't call method "execute" on an undefined value at postinstall line 20.