Well i got it fast ready here is the updated attiny84 core file
Attiny84
The attiny84 does not have a uart/serial port, so making a bootloader is much harder, But i will try this.
I also tested with the arduinoISP for you, and i got it working.
So you dont need a bootloader, and you can upload with the arduino IDE
But there are some step's you need to do (copy/past from the readme)
If you dont have a ISP programmer you can use the arduino Examples ArduinoISP
Upload that sketch to a normal arduino, see http://arduino.cc/en/Tutorial/ArduinoISP
And Connect arduinopin 13 to CLK, 12 to MISO, 11 to MOSI and 10 to RESET
Also hook up the 5V+ and GND. For those line on a attiny, check the datasheet @ atmel.com
for the 14pdip it's:
pin 1 5V
pin 4 RESET (Needs a 10K resistor in parrallel with 5V+)
pin 7 MOSI
pin 8 MISO
pin 9 CLK
pin 14 GND
+-\/-+
VCC 1| |14 GND
(D0) PB0 2| |13 AREF
(D1) PB1 3| |12 PA1 (D9)
RESET 4| |11 PA2 (D8)
INT0 PWM (D2) PB2 5| |10 PA3 (D7)
PWM (D3) PA7 6| |9 PA4 (D6)
PWM (D4) PA6 7| |8 PA5 (D5) PWM
+----+
I just found out that you can set this parameter in boards.txt, so when you selected the attiny84, it will use automatic the arduinoIsp
So you don't have to change your preference file.
This is updated in the latest 03 version
Next you have to edit your preference file, and change the upload.using=bootloader to upload.using=arduinoisp
see http://arduino.cc/en/Hacking/Programmer for more info
Now you can upload to the atting84 without bootloader 
remember when you want to upload to a normal arduino, you have to change the preference file again to bootloader