deps: update old and remove unused dependencies

This commit updates all of the dependencies in package.json to
their most recent versions. It also removes dependencies that were
specified in package.json but not used - or only used in a
`require()` statement.

These changes have some ripple effects. Istanbul has not been
supported for some time, so it has been replaced with nyc.
The code coverage reporting tool from codacy has been updated
as well. This could not be tested without having the API token.

Finally, the CI job has been modified to run tests on Node.js
versions 10x and 12x. All older versions of Node.js are no longer
maintained.

Signed-off-by: Lance Ball <[email protected]>

Author: lance

.travis.yml

@@ -1,13 +1,12 @@
 language: node_js
 node_js:
-- 8
-- 7
-- 6
+- 12
+- 10
 cache: npm
 jobs:
   include:
   - stage: github release
-    node_js: '6'
+    node_js: '12'
     deploy:
       provider: releases
       api_key:
@@ -17,7 +16,7 @@ jobs:
         tags: true
 
   - stage: npm release
-    node_js: '6'
+    node_js: '12'
     deploy:
       provider: npm
       email: [email protected]

lib/bindings/http/emitter_binary.js

@@ -1,5 +1,4 @@
 var axios = require("axios");
-var empty = require("is-empty");
 
 const Constants = require("./constants.js");
 

lib/specs/spec_0_2.js

@@ -1,5 +1,4 @@
 var uuid  = require("uuid/v4");
-var empty = require("is-empty");
 var Ajv   = require("ajv");
 
 // Reserved attributes names

lib/specs/spec_0_3.js

@@ -1,5 +1,4 @@
 const uuid  = require("uuid/v4");
-const empty = require("is-empty");
 const Ajv   = require("ajv");
 
 const {

lib/specs/spec_1.js

@@ -1,7 +1,5 @@
 const uuid  = require("uuid/v4");
-const empty = require("is-empty");
 const Ajv   = require("ajv");
-const URI   = require("uri-js");
 
 const {
   asData,