• download and install CH340g driver (check your FTDI chip)
• install CoolTerm (http://freeware.the-meiers.org/)
• install ESPlorer (http://esp8266.ru/esplorer/)
• open CoolTerm, options, choose appropriate /dev/cu.* port and connect

To flash

• download firmware
• Install esptool

git clone https://github.com/themadinventor/esptool.git 
cd esptool
sudo python ./setup.py install

• upgrade firmware

$ python ./esptool.py --port=/dev/cu.wchusbserial620  write_flash  -fm=dio -fs=32m 0x00000 /tmp/nodemcu_integer_0.9.6-dev_20150704.bin

Connecting...
Erasing flash...
Took 3.92s to erase flash block
Wrote 450560 bytes at 0x00000000 in 54.1 seconds (66.6 kbit/s)...

Leaving...