Build superagent.js from fresh HEAD.

To avoid clutter after changes are applied.
Increase node tests timeout duration.
Change basic tests echo endpoint method to all.

The echo endpoint is handy for testing request headers received by the server, it will echo the headers in return, but it used to only accept POST HTTP methods. Changing it to accept all methods makes it more re-usable in other scenarios as well.
Add xml to mime types mappings.

In the same way that json maps to application/json and html maps to text/html now too xml will expand to application/xml when substituted.
Only missing from the browser lookup table as the node.js scripts use mime.lookup(type) to accomplish the same.
Add request .accept(type) method.

In the same fashion of the .type() method which is used to set the Content-Type header we now can utilize the the .accept() method to do the same for the Accept request header.
Tests added for .accept() and application/xml
Re-build superagent.js with updated functionality.

Because we started with a clean build this commit now only adds the new changes.
Update History.md with new release changelog.
Merge branch 'master' of git://github.com/nickl-/superagent into nickl--master

* 'master' of git://github.com/nickl-/superagent:
  Update History.md with new release changelog.
  Re-build superagent.js with updated functionality.
  Tests added for .accept() and application/xml
  Add request .accept(type) method.
  Add xml to mime types mappings.
  Change basic tests echo endpoint method to all.
  Increase node tests timeout duration.
  Build superagent.js from fresh HEAD.
add new standalone build