drivers: Initial import of SPI low-level driver IF
drivers: fixes to the SPI low-level interface
driver: updated SPI driver interface
[SQUASH ME] added fixed speed values
[SQUASH ME] removed UNDEFINED from device list
[SQUASH ME] fixed signature of spi_transfer_reg()
[SQUASH ME] added begin_transaction, fixed doc
.astylerc: Respect max code line length of 100
Merge pull request #1536 from krf/fix-astylerc

.astylerc: Respect max code line length of 100
cpu/nrf51822: squash added support for nrf51822 cpu
boards/pca10000: squash added support for Nordic Dev Kit p1
boards/pca10005: squash added Support for Nordic Dev Kit p2
Merge pull request #1498 from fukuehl/nrf51822

cpu/board: added support for nrf51822
Merge pull request #1311 from haukepetersen/add_driver_spi_if

drivers: Initial import of SPI low-level driver IF
cpu: atmega_common: Initial import
cpu: atmega2560: Initial import
board: arduino-mega2560: Initial import
tests: blacklist board arduino-mega2560:

    - tests/bloom: value too large for field of 2 bytes
    - tests/<other>: missing headers (time.h or sys/types.h)
test: add download of avr toolchain to .travis.yml
tests: blacklist tests/test_coap and examples that fail due to missing header files