Added Rick Osborne's super-easy gitflow installer oneliner to the project.

See the README file for instructions on how to use it.
diff --git a/contrib/gitflow-installer.sh b/contrib/gitflow-installer.sh
new file mode 100644
index 0000000..33dbe58
--- /dev/null
+++ b/contrib/gitflow-installer.sh
@@ -0,0 +1,78 @@
+#!/bin/sh
+
+# git-flow make-less installer for *nix systems, by Rick Osborne
+# Based on the git-flow core Makefile:
+# http://github.com/nvie/gitflow/blob/master/Makefile
+
+# Licensed under the same restrictions as git-flow:
+# http://github.com/nvie/gitflow/blob/develop/LICENSE
+
+# Does this need to be smarter for each host OS?
+if [ -z "$INSTALL_PREFIX" ] ; then
+	INSTALL_PREFIX="/usr/local/bin"
+fi
+
+if [ -z "$REPO_NAME" ] ; then
+	REPO_NAME="gitflow"
+fi
+
+if [ -z "$REPO_HOME" ] ; then
+	REPO_HOME="http://github.com/nvie/gitflow.git"
+fi
+
+EXEC_FILES="git-flow"
+SCRIPT_FILES="git-flow-init git-flow-feature git-flow-hotfix git-flow-release git-flow-support git-flow-version gitflow-common gitflow-shFlags"
+SUBMODULE_FILE="gitflow-shFlags"
+
+echo "### gitflow no-make installer ###"
+
+case "$1" in
+	uninstall)
+		echo "Uninstalling git-flow from $INSTALL_PREFIX"
+		if [ -d "$INSTALL_PREFIX" ] ; then
+			for script_file in $SCRIPT_FILES $EXEC_FILES ; do
+				echo "rm -vf $INSTALL_PREFIX/$script_file"
+				rm -vf "$INSTALL_PREFIX/$script_file"
+			done
+		else
+			echo "The '$INSTALL_PREFIX' directory was not found."
+			echo "Do you need to set INSTALL_PREFIX ?"
+		fi
+		exit
+		;;
+	help)
+		echo "Usage: [environment] gitflow-installer.sh [install|uninstall]"
+		echo "Environment:"
+		echo "   INSTALL_PREFIX=$INSTALL_PREFIX"
+		echo "   REPO_HOME=$REPO_HOME"
+		echo "   REPO_NAME=$REPO_NAME"
+		exit
+		;;
+	*)
+		echo "Installing git-flow to $INSTALL_PREFIX"
+		if [[ -d "$REPO_NAME" && -d "$REPO_NAME/.git" ]] ; then
+			echo "Using existing repo: $REPO_NAME"
+		else
+			echo "Cloning repo from GitHub to $REPO_NAME"
+			git clone "$REPO_HOME" "$REPO_NAME"
+		fi
+		if [ -f "$REPO_NAME/$SUBMODULE_FILE" ] ; then
+			echo "Submodules look up to date"
+		else
+			echo "Updating submodules"
+			lastcwd=$PWD
+			cd "$REPO_NAME"
+			git submodule init
+			git submodule update
+			cd "$lastcwd"
+		fi
+		install -v -d -m 0755 "$INSTALL_PREFIX"
+		for exec_file in $EXEC_FILES ; do
+			install -v -m 0755 "$REPO_NAME/$exec_file" "$INSTALL_PREFIX"
+		done
+		for script_file in $SCRIPT_FILES ; do
+			install -v -m 0644 "$REPO_NAME/$script_file" "$INSTALL_PREFIX"
+		done
+		exit
+		;;
+esac