Adds content type support in S3

src/Adapters/Files/FilesAdapter.js

@@ -12,7 +12,7 @@
 // database adapter.
 
 export class FilesAdapter {
-  createFile(config, filename, data) { }
+  createFile(config, filename: string, data, contentType: string) { }
 
   deleteFile(config, filename) { }
 

src/Adapters/Files/GridStoreAdapter.js

@@ -28,7 +28,7 @@ export class GridStoreAdapter extends FilesAdapter {
 
   // For a given config object, filename, and data, store a file
   // Returns a promise
-  createFile(config, filename: string, data) {
+  createFile(config, filename: string, data, contentType: string) {
     return this._connect().then(database => {
       let gridStore = new GridStore(database, filename, 'w');
       return gridStore.open();

src/Adapters/Files/S3Adapter.js

@@ -68,7 +68,7 @@ export class S3Adapter extends FilesAdapter {
 
   // For a given config object, filename, and data, store a file in S3
   // Returns a promise containing the S3 object creation response
-  createFile(config, filename, data) {
+  createFile(config, filename, data, contentType) {
     let params = {
       Key: this._bucketPrefix + filename,
       Body: data
@@ -76,6 +76,9 @@ export class S3Adapter extends FilesAdapter {
     if (this._directAccess) {
       params.ACL = "public-read"
     }
+    if (contentType) {
+      params.ContentType = contentType;
+    }
     return this.createBucket().then(() => {
       return new Promise((resolve, reject) => {
         this._s3Client.upload(params, (err, data) => {