Cleaned up 'has' and 'is' checks and tests using them in exports.zsh.

The conditional `if [[ -x ... ]]` tests to see if the named file
exists and is executable. Having &>/dev/null appended to the the end
of the -x checks was preventing them from working properly.

Wrapped sourcing of virtualenvwrapper.sh in newly created $HAS_VIRTUALENV
test.

	modified:   .zsh/checks.zsh
	modified:   .zsh/exports.zsh
Cloned and edited gitconfig to make remote version.

Needed a gitconfig for machines where I can install my preferred tools
and need to use vim as editor and vimdiff as the merge and diff tool.
Created gitconfig_remote for that purpose.
updated README regarding gitconfig_remote