Add IPFS service

Add the `ipfs-api` JS library and a service using the browserified
version of it. The service has functions for storing and reading file
contests.

app/services/ipfs.js

@@ -0,0 +1,32 @@
+import Ember from 'ember';
+import ipfsAPI from 'npm:ipfs-api';
+import config from 'kredits-web/config/environment';
+
+export default Ember.Service.extend({
+
+  ipfsInstance: null,
+
+  ipfs: function() {
+    if (this.get('ipfsInstance')) {
+      return this.get('ipfsInstance');
+    }
+    let ipfs = ipfsAPI(config.ipfs);
+    this.set('ipfsInstance', ipfs);
+    window.ipfs = ipfs;
+    return ipfs;
+  }.property('ipfsInstance'),
+
+  storeFile(content) {
+    let ipfs = this.get('ipfs');
+    return ipfs.add(new ipfs.Buffer(content)).then((res) => {
+      return res[0].hash;
+    });
+  },
+
+  getFile(hash) {
+    return this.get('ipfs').cat(hash, { buffer: true }, (err, res) => {
+      return res.toString();
+    });
+  }
+
+});

app/services/kredits.js

@@ -7,6 +7,8 @@ import kreditsContracts from 'npm:kredits-contracts';
 
 export default Ember.Service.extend({
 
+  ipfs: Ember.inject.service(),
+
   web3Instance: null,
   web3Provided: false, // Web3 provided (using Mist Browser, Metamask et al.)