Fix Windows colors: %ENV instead of exec prefix

Tested with GitHub for Windows 1.0.36.0 using cmd, Powershell, and Git
bash.
Coloration worked properly in all three environments. Git bash threw a
harmless "Unsuccessful stat on filename containing newline" warning, but
otherwise worked. (I blame the ancient perl included with msysgit.)

By adding a batch script launcher, we can thereby remove all the Windows
caveat documentation in the README file. To use eg, simply put this
directory
in your path, even on Windows.
Fix eg commit on Windows. eg_exec requires a perl executable.
Fix eg on Strawberry Perl.

Strawberry Perl presents $ENV{PATH} with semicolons instead of
colons. Just skip examining the path directly and just try to run
git.
Fix msys Perl warning in eg log
updated regex for git 1.8 messaging
version bump to 1.8.0