Make some changes suggested by Tomi Ollila [1]. Changes: v3 since v2: * Use read function instead of cat(1) to read counter value. * Add a newline after the count value in state file and notmuch_counter_value() output. v2 since v1: * Rename $notmuch_counter variable to $notmuch_counter_command. * Rename notmuch_counter() function to notmuch_counter_value(). * Fix documentation for notmuch_counter_value(). * Removed unneeded and add missing "|| return" in notmuch_counter_reset(). * Coding style fixes. [1] id:"yf6aa7gj7w5.fsf@taco2.nixu.fi"