Propagete connection failure properly

It was parsed as;
  raise_error();
  "foo" + "bar"
Let net/http handle HTTP_PROXY

td command no longer care about HTTP_PROXY.

The previous code for stream_fetch modifies URI when HTTP_PROXY is set;
  https://foo/ -> http://foo:443/
This caused accessing SSL server port with plain text protocol which
fails always.
Avoid singleton method of Updater for ease-of-test
Add Updater test for proxy
Move methods that needs to be module_function
Add jar_update test
Remove unused fixture file
Merge pull request #30 from treasure-data/bugfix_update_with_proxy

Make updater work with http_proxy