From Release Notes:
ARDUINO 1.6.7 - 2015.12.17
* New arduino-builder: faster, better prototype generation and library discovery logic, and more. See https://github.com/arduino/arduino-builder/compare/1.0.5...1.3.9
* Serial plotter now allows to plot multiple values at once. Thanks @henningpohl
* New translations
* Added support to file:// protocol for boards manager URLs
* Portable sketchbook folder can now be any arbitrary location
* Fixed a bug that caused Boards Manager to install the same tool twice or more, thus wasting disk space, if other cores where using tools delivered by arduino
* Fixed various Boards manager glitches, in particular when removing a board
* Windows: Arduino IDE icon is now in high definition, bye bye that blurry icon
* Remote upload without SSH is now supported (allows OTA upload for many 3rd party boards). Thanks @me-no-dev.
* SPI: Added SPI.transfer16(...) function to SAM core.
* Ethernet, WiFi, SoftwareSerial: Fixed flush() behaviour:
the flush function is no more dropping the receive buffer, as per
1.0 API specification. Thanks @drmpf
* Fixed wrong timings for HardwareSerial::flush() in SAM core. Thanks @borisff
* Stream: Optional lookahead and skipChar options added to parseInt and parseFloat,
parseFloat also support parsing floats without a leading 0,
Stream::find(char) added to SAM. Thanks @Chris--A.
* Leonardo/Micro (and other atmega32u4 based boards) now have SerialUSB alias for Serial
* Leonardo now has LED_BUILTIN_RX/TX definitions in variant file. Thanks @NicoHood
*** This bug has been marked as a duplicate of bug 525882 ***