Revert "Use 0.0.0.0 rather than user specific IP address."

Reverts taf2/curb#187

multiple tests fail when we make this change... need to rethink

```
  1) Error:
test_post_multipart_array_remote(TestCurbCurlEasy):
Curl::Err::ReadError: Failed to open/read local data from file/application
    /Users/taf2/work/curb/lib/curl/easy.rb:72:in `perform'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:651:in `http_post'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:651:in `test_post_multipart_array_remote'

  2) Error:
test_post_multipart_file_remote(TestCurbCurlEasy):
Curl::Err::ReadError: Failed to open/read local data from file/application
    /Users/taf2/work/curb/lib/curl/easy.rb:72:in `perform'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:678:in `http_post'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:678:in `test_post_multipart_file_remote'

  3) Error:
test_post_streaming(TestCurbCurlEasy):
Curl::Err::ReadError: Failed to open/read local data from file/application
    /Users/taf2/work/curb/lib/curl/easy.rb:72:in `perform'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:866:in `http_post'
    /Users/taf2/work/curb/tests/tc_curl_easy.rb:866:in `test_post_streaming'
```