Upgrade lodash and gulp

.babelrc

@@ -1,3 +1,3 @@
 {
-  "presets": ["es2015"]
+  "presets": ["env"]
 }

.travis.yml

@@ -1,9 +1,8 @@
 language: node_js
 node_js:
-  - "4"
-  - "5"
-  - "6"
-  - "7"
+  - "8"
+  - "10"
+  - "12"
 install:
   - yarn install
 script:

gulpfile.babel.js

@@ -5,10 +5,9 @@ import eslint from 'gulp-eslint';
 import babel from 'gulp-babel';
 import plumber from 'gulp-plumber';
 import istanbul from 'gulp-babel-istanbul';
-import util from 'gulp-util';
+import log from 'fancy-log';
 import del from 'del';
 import Instrumenter from 'isparta';
-import runSequence from 'run-sequence';
 
 const paths = {
   sourceFiles: ['src/**/*.js'],
@@ -21,9 +20,7 @@ paths.buildFiles = [`${paths.buildDir}/**/*.js`];
 /**
  * Task to remove assets from last build
  */
-gulp.task('clean', (done) => {
-  del(['build', 'coverage'], done);
-});
+gulp.task('clean', () => del(['build', 'coverage']));
 
 /**
  * Task to lint the src files
@@ -46,7 +43,7 @@ gulp.task('build', () => (
     }))
     .pipe(sourcemaps.write())
     .pipe(gulp.dest(paths.buildDir))
-    .on('error', util.log)
+    .on('error', log)
 ));
 
 /**
@@ -72,7 +69,7 @@ gulp.task('test', () => (
       require: 'babel-register',
       reporter: 'list',
     }))
-    .on('error', util.log)
+    .on('error', log)
 ));
 
 gulp.task('coverage:report', () => (
@@ -90,12 +87,10 @@ gulp.task('coverage:report', () => (
       },
     }))
     .pipe(istanbul.enforceThresholds({ thresholds: { global: 10 } }))
-    .on('error', util.log)
+    .on('error', log)
 ));
 
-gulp.task('test:coverage', done => (
-  runSequence('coverage:instrument', 'test', 'coverage:report', done)
-));
+gulp.task('test:coverage', gulp.series('coverage:instrument', 'test', 'coverage:report'));
 
 /**
  * Task to watch the files whilst developing
@@ -105,6 +100,6 @@ gulp.task('watch', () => (
 ));
 
 
-gulp.task('prebuild', ['clean', 'lint', 'test:coverage']);
-gulp.task('default', ['prebuild', 'build']);
-gulp.task('prepublish', ['default']);
+gulp.task('prebuild', gulp.series('clean', 'lint', 'test:coverage'));
+gulp.task('default', gulp.series('prebuild', 'build'));
+gulp.task('prepare', gulp.series('default'));