Peel the zest off the lime with a vegetable peeler in strips. Put in a large saucepan; add the juice of the lime and the remaining ingredients. Bring to a boil. Lower the heat so that the mixture boils moderately for 60 – 70 minutes. It will have reduced down in volume and thickened slightly, it will thicken more as it cools. Taste – if you want it sweeter you can add a little more agave while it is still warm, just stir it in. Pour into a bottle or jar and let cool. Store in the refrigerator for up to 2 weeks.