feat: Switch to function-based specification of dependencies

Allows dependencies to be economically expressed and used.
  For example, see the new definition of subtract.
  Credit for the basic idea goes to James Drew, see
  https://stackoverflow.com/a/41525264

  Resolves #21.

src/complex/add.mjs

@@ -1,13 +1,10 @@
 export {Types} from './Types/Complex.mjs'
 
 export const add = {
-   '...Complex': {
-      uses: ['self'],
-      does: ref => addends => {
-         if (addends.length === 0) return {re:0, im:0}
-         const seed = addends.shift()
-         return addends.reduce((w,z) =>
-            ({re: ref.self(w.re, z.re), im: ref.self(w.im, z.im)}), seed)
-      }
+   '...Complex': ({self}) => addends => {
+      if (addends.length === 0) return {re:0, im:0}
+      const seed = addends.shift()
+      return addends.reduce(
+         (w,z) => ({re: self(w.re, z.re), im: self(w.im, z.im)}), seed)
    }
 }

src/complex/complex.mjs

@@ -5,7 +5,7 @@ export const complex = {
     * have a numeric/scalar type, e.g. by implementing subtypes in
     * typed-function
     */
-   'any, any': {does: (x, y) => ({re: x, im: y})},
+   'any, any': () => (x, y) => ({re: x, im: y}),
    /* Take advantage of conversions in typed-function */
-   Complex: {does: z => z}
+   Complex: () => z => z
 }

src/complex/negate.mjs

@@ -1,10 +1,5 @@
 export {Types} from './Types/Complex.mjs'
 
 export const negate = {
-   Complex: {
-      uses: ['self'],
-      does: ref => z => {
-         return {re: ref.self(z.re), im: ref.self(z.im)}
-      }
-   }
+   Complex: ({self}) => z => ({re: self(z.re), im: self(z.im)})
 }