WIP: major progress for #101

- feat(www): implement preprocessor for FormData instances
- feat(www): implement API checks for multipart requests
- feat(android): implement multipart requests
- chore(specs): implement www specs for new prprocessor

test/mocks/FileReader.mock.js

@@ -0,0 +1,39 @@
+module.exports = class FileReaderMock {
+  constructor() {
+    this.EMPTY = 0;
+    this.LOADING = 1;
+    this.DONE = 2;
+
+    this.error = null;
+    this.onabort = () => {};
+    this.onerror = () => {};
+    this.onload = () => {};
+    this.onloadend = () => {};
+    this.onloadstart = () => {};
+    this.onprogress = () => {};
+    this.readyState = this.EMPTY;
+    this.result = null;
+  }
+
+  readAsArrayBuffer(file) {
+    this.readyState = this.LOADING;
+    this.onloadstart();
+    this.onprogress();
+    this.result = file._buffer;
+    this.readyState = this.DONE;
+    this.onloadend();
+    this.onload();
+  }
+
+  readAsBinaryString() {
+    throw new Error('Not implemented in FileReaderMock.');
+  }
+
+  readAsDataUrl() {
+    throw new Error('Not implemented in FileReaderMock.');
+  }
+
+  readAsText() {
+    throw new Error('Not implemented in FileReaderMock.');
+  }
+}