ci: remove travis & appveyor (#314)

Author: erisu

.appveyor.yml

@@ -21,10 +21,6 @@ description: Upload and download files.
 #         under the License.
 -->
 
-|AppVeyor|Travis CI|
-|:-:|:-:|
-|[![Build status](https://ci.appveyor.com/api/projects/status/github/apache/cordova-plugin-file-transfer?branch=master)](https://ci.appveyor.com/project/ApacheSoftwareFoundation/cordova-plugin-file-transfer)|[![Build Status](https://travis-ci.org/apache/cordova-plugin-file-transfer.svg?branch=master)](https://travis-ci.org/apache/cordova-plugin-file-transfer)|
-
 # cordova-plugin-file-transfer
 
 # Usage notice