Handling post requests for Accel servlet (issue1822041)

[gagan . goku]

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


Please review this at http://codereview.appspot.com/1822041/show

Affected files:
  main/java/org/apache/shindig/gadgets/http/BasicHttpFetcher.java
  main/java/org/apache/shindig/gadgets/servlet/AccelHandler.java
  main/java/org/apache/shindig/gadgets/servlet/HtmlAccelServlet.java
  main/java/org/apache/shindig/gadgets/uri/UriUtils.java
  test/java/org/apache/shindig/gadgets/servlet/HtmlAccelServletTest.java