Fix warning-mode nitpicks

[wconrad]

Eliminate -w warnings. Most of these are just in the tests, but a few are encountered when using httpclient.

To see the warnings:

ruby -w bundle exec test/runner.rb

The warnings were:

/home/wayne/lab/httpclient/test/test_auth.rb:233: warning: assigned but unused variable - threads
/home/wayne/lab/httpclient/test/test_auth.rb:254: warning: ambiguous first argument; put parentheses or a space even after `/' operator
/home/wayne/lab/httpclient/test/test_auth.rb:270: warning: ambiguous first argument; put parentheses or a space even after `/' operator
/home/wayne/.rvm/gems/ruby-2.2.1/gems/httpclient-2.6.0.1/lib/httpclient.rb:1083: warning: assigned but unused variable - e
/home/wayne/.rvm/gems/ruby-2.2.1/gems/httpclient-2.6.0.1/lib/httpclient/auth.rb:538: warning: assigned but unused variable - domain_uri
/home/wayne/lab/httpclient/test/test_auth.rb:127: warning: method redefined; discarding old data_size
/home/wayne/.rvm/gems/ruby-2.2.1/gems/rubyntlm-0.5.0/lib/net/ntlm/security_buffer.rb:42: warning: previous definition of data_size was here
/home/wayne/lab/httpclient/test/test_webagent-cookie.rb:443: warning: shadowing outer local variable - f
/home/wayne/lab/httpclient/test/test_cookie.rb:293: warning: shadowing outer local variable - f
/home/wayne/lab/httpclient/test/test_httpclient.rb:773: warning: shadowing outer local variable - res
/home/wayne/lab/httpclient/test/test_httpclient.rb:786: warning: assigned but unused variable - res
/home/wayne/lab/httpclient/test/test_httpclient.rb:803: warning: assigned but unused variable - res
/home/wayne/lab/httpclient/test/test_httpclient.rb:958: warning: assigned but unused variable - res
/home/wayne/lab/httpclient/test/test_httpclient.rb:975: warning: assigned but unused variable - res
/home/wayne/lab/httpclient/test/test_httpclient.rb:1246: warning: assigned but unused variable - res

[wconrad]

I don't think the Traviis test failures are caused by this PR. The tests pass on my box with these ruby versions:

• ruby-head (ruby 2.3.0dev (2015-06-06 trunk 50791) [x86_64-linux])
• ruby-2.2.1
• jruby-1.7.19

jruby-head, I don't know about... I can't get it to build.

[nahi]

Thank you very much. I didn't know I made so much bad code :-(