Generate a config for truffle.js networks -> development, instead of modifying pre-existing

exec.js

@@ -104,9 +104,13 @@ try {
   // Coverage network opts NOT specified: default to the development network w/ modified
   // port, gasLimit, gasPrice. Export the config object only.
   } else {
-    truffleConfig.networks.development.port = port;
-    truffleConfig.networks.development.gas = gasLimitHex;
-    truffleConfig.networks.development.gasPrice = gasPriceHex;
+    truffleConfig.networks.development = {
+      host: "localhost",
+      network_id: "*", 
+      port: port,
+      gas: gasLimitHex,
+      gasPrice: gasPriceHex
+    }
     coverageOption = '';
     fs.writeFileSync(`${coverageDir}/truffle.js`, `module.exports = ${JSON.stringify(truffleConfig)}`);
   }