Adding capability in AbsolutePathReferenceVisitor to resolve relative to base tag url (issue1726041)

[ga...@gmail.com]

Reviewers: johnfargo, zhoresh, shindig.remailer_gmail.com,  
dev-remailer_shindig.apache.org,

Message:
Synced to r955719.


Description:
Adding capability in AbsolutePathReferenceVisitor to resolve relative to
base tag url
Base tag url looks like this:
<base href="http://www.google.com/">

And then any resource like:
<img src="/hello.jpg">
should be resolved to "http://www.google.com/hello.jpg"


Please review this at http://codereview.appspot.com/1726041/show

Affected files:
   M      
java/gadgets/src/main/java/org/apache/shindig/gadgets/rewrite/AbsolutePathReferenceVisitor.java
   M      
java/gadgets/src/test/java/org/apache/shindig/gadgets/rewrite/AbsolutePathReferenceVisitorTest.java