Rename healthcheck to preflight

lib/kredits.js

@@ -1,7 +1,7 @@
 const ethers = require('ethers');
 const RSVP = require('rsvp');
 
-const Healthcheck = require('./utils/healthcheck');
+const Preflight = require('./utils/preflight');
 
 const ABIS = {
   Contributors: require('./abis/Contributors.json'),
@@ -97,8 +97,8 @@ class Kredits {
     return this.contracts[name];
   }
 
-  healthcheck() {
-    return new Healthcheck(this).check();
+  preflightChecks() {
+    return new Preflight(this).check();
   }
 }