Tail Flash

Added a tail flash when entering and exiting locked mode so you know if
you got it right.
Merge pull request #52 from mcsarge/master

Tail Flash
Update README.md
SOS Rewrite

Re write the way that SOS is flashed.
Changed the nightlight to turn off the tail cap LED when the main light
is on. Switch nightlight to use the green tail cap LED instead of the
red.
Update README.md
More tuning to Mode SOS

Changed the inter-word delay to be an exactly 7 beats and updated the
comments to explain how the bitmap is used to create the dits and dahs.
Also re-ordered all the constants at the top of the program.
Removed unused setting of bit BLOCK_TURNING_OFF as it is never read by
the program.
Move the declaration of time to the start of the program and simple
reset the time at each run through the loop.
Replaced some of the DBG code so it will be compiled in when the
appropriate define is set.
Renamed tailflash to tailflashesLeft because it tells what the variable
is really doing.
Merge branch 'master' of https://github.com/mcsarge/hexbright
New feature of Locked Mode and documentation updates.

Added code that causes the light to flash the tail cap LED 2 times if
the light is in locked mode and the button is pressed.
Update README.md
Various Documentation Updates
Merge pull request #53 from mcsarge/master

Various Changes in Locked Mode and SOS with Documentation Updates
port new lock mode and sos mode from set_and_remember