Update node dependencies + fix breaking changes

-All node dependencies are up-to-date in package.json
-Updated semantic versioning of some node dependencies in package.json
-Applied fixes to necessary explorer files to fix breaking changes to mongoose dependency
-Update README with new Node.js and MongoDB version recommendations

NOTE: Node.js must be updated to at least v14.13.1 to fix breaking errors in a few of the updated dependencies

lib/database.js

@@ -214,7 +214,7 @@ function hex_to_ascii(hex) {
 module.exports = {
   // initialize DB
   connect: function(database, cb) {
-    mongoose.connect(database, { useNewUrlParser: true, useCreateIndex: true, useUnifiedTopology: true, useFindAndModify: false }, function(err) {
+    mongoose.connect(database, function(err) {
       if (err) {
         console.log('Unable to connect to database: %s', database);
         console.log('Aborting');