Can't Flash ESP8266 latest firmware, says "Fast Flashing error" and "Invalid head of packet(' ')

Question

I can't figure out how to flash the firmware found on http://www.electrodragon.com/w/ESP8266_AT-Command_firmware. I am using ESP8266 Download tool v3.4.4. When I am adding a firmware in download path it goes on till a fixed percentage (77 or 99..mostly) and gives the error Invalid head of packet, FAST FLASHING ERROR. One more thing is that the tutorials I am using to do this have many download path entries filled in the download tool while mine are just blank. It says upload the combined file to 0x0000. I tried uploading V1.54... file's content (both files) but still got the similar error(https://i.stack.imgur.com/wiQ5K.png). :P

So anyone could just guide me through this as I am a complete newb into this. Please mention any other information needed in comments.

PS

1. I am pretty sure the power supply is adequate as I have been using esp8266 with the old firmware smoothly. I have also connected a 200uF capacitor b/w gnd and vcc(3.3v from FTDI).
2. I have double checked the connections.(Yes, GPIO0 is grounded).
3. I flashed an earlier version successfully ai-thinker-v1.1.1.bin but when I connected it to arduino IDE serial monitor it started giving unending gibberish text :P.