Unit Test - contentreader.go

Add unit tests to validate methods under utils package which are defined in [contentreader.go](https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/utils/contentreader.go).

All unit tests should go in contentreader_test.go under [utils/](https://github.com/apache/incubator-openwhisk-wskdeploy/blob/master/utils)

```
// read content from a file or web page depending on the "prefix" of the location
func Read(url string) (content []byte, err error) {
...
}
```