Summary:

Previsouly this code would allow only a single script to run:

```
	r.Get("/swagger/*", httpSwagger.Handler(
		httpSwagger.BeforeScript("console.log('before 1')"),
		httpSwagger.BeforeScript("console.log('before 2')"),
		httpSwagger.URL("http://localhost:1323/swagger/doc.json"), //The url pointing to API definition
	))

	// Only 'before 2' will be printed
```

Now both scripts are run:

```
'before 1'
'before 2'
```

This improves behavior of BeforeScript and AfterScript. If users
want to provide multiple scripts, they are forced to combine them using
strings.

Closes swaggo#81

Test Plan: Updated existing example and tests. Added new test TestMultipleScripts