spring-boot-tools LaunchedURLClassLoader getUrls() returns invalid jar:file: urls on windows
I have a spring boot (1.0.0.RC3) application with an embedded jetty (9.1.0.v20131115). 

When trying to start on windows, while on Linux works normally, I get this exception on jetty WebAppContext startup:

```
java.net.URISyntaxException: Illegal character in opaque part at index 11: 
```

While debugging I noticed that the urls returned from LaunchedURLClassLoader.getUrls() on line 97 of org.eclipse.jetty.webapp.WebInfConfiguration are in this format (note the single backslash):

```
jar:file:C:\path_to_jar.jar!/webapp
```

I could workaround the problem by extending WebInfConfiguration changing line 110 from:

```
containerUris[i] = new URI(u.toString().replaceAll(" ", "%20"));
```

to

```
containerUris[i] = new URI(u.toString().replaceAll(" ", "%20").replace('\\', '/'));
```

and:

```
WebAppContext ctx = new WebAppContext();
ctx.setConfigurationClasses(new String[] {   
    "au.com......MyEmbeddedWebInfConfiguration",  [... default classes ...] });
```

Is  jar:file:C:\path_to_jar.jar!/webapp a valid URL at all? 
Shouldn't it be with escaped backslashes or forward slashes?
