Minor package.json tweaks, update .travis.yml and dependencies (#31)

* Refactor package.json properties.

* Update Travis config.

* test node.js node 8 and remove 5 and 4.0
* cache the node_modules folder
* switch to double quotes

* Update dependencies.

* Add package-lock.json.

* Clean up .gitignore to the bare minimum.

.gitignore

@@ -1,36 +1,3 @@
-# Logs
-logs
-*.log
-npm-debug.log*
-
-# Runtime data
-pids
-*.pid
-*.seed
-
-# Directory for instrumented libs generated by jscoverage/JSCover
-lib-cov
-
-# Coverage directory used by tools like istanbul
-coverage
-
-# Grunt intermediate storage (http://gruntjs.com/creating-plugins#storing-task-files)
-.grunt
-
-# node-waf configuration
-.lock-wscript
-
-# Compiled binary addons (http://nodejs.org/api/addons.html)
-build/Release
-
-# Dependency directory
-node_modules
-
-# Optional npm cache directory
-.npm
-
-# Optional REPL history
-.node_repl_history
-
-# for binary install
+/node_modules/
 /vendor/
+/npm-debug.log