Remove XBEE_MODE_API.
Correct some comments.
Use SoftwareSerial module if debug is on.
Use software serial module when debbuging on.
Xively spec says the minimum interval of sending data is 5 seconds, so set 6 seconds as main loop interval.
Add solar panel image file.
Merge branch 'software_serial'
Modify sign value from '0 or 1' to '1 or -1'.