Added functions getDeviceFriendlyName() and getDevices(). 

getDeviceFriendlyName
Argument: Serial Number
Returns the device's friendly name if set, else returns DEVICE_WITH_NO_NAME

getDevices() - Useful in multi-device scenarios. Returns an array of serials found.
added serial_number check as proposed by gboudreau
Fixing getEnergyLatest() (Nest endpoint now require a jsonp parameter...)
Fixes #20
Added enableHumidifier(boolean) method to start and stop the humidifier

Fix #22
Documenting recent addition of humidifier setter
Better errors handling: now trowing RuntimeException with a relevant error description, and one of NESTAPI_ERROR_* constant as the error code.
Added setter for away min & max temperatures
Fixed getEnergyLatest

Fixes #23
Added setter for Auto-Away
Merge pull request #19 from rkaramchedu/master

Added two new functions
Added note on auto_away possible values
Added 'name' property to getDeviceInfo; added getDevices() to examples