fix bin/httparty + cucumber tests for it

It looks, that there is no tests for ```bin/httparty```, so i created tests for it.
__Changes:__
1) Without 
```ruby
puts JSON.pretty_generate(response.delegate)
```
tests are failed ( delegate method is undefined)

2) For testing bin/httparty i am using [aruba - cucumber extension for testing command line apps](https://github.com/cucumber/aruba).

3) We need explicitly run port in featurers:
```ruby
Scenario: Make a get request
  Given a remote deflate service on port '4001'
```
so, i run mongrel server each scenario with different port for each scenario
```ruby
Given /^a remote deflate service on port '(\d+)'/ do |port|
 run_server(port)
 @handler = DeflateHandler.new
end
```
Notice: On other tests(which are now on master branch), different port are assigned too for each scenario, but implicitly here:
```ruby
def new_port
  server = TCPServer.new('0.0.0.0', nil)
  port = server.addr[1]
ensure
  server.close
end
```
4) Also i update cucumber to stable release, and move it to test group in Gemfile because there are a lot of changes since 0.7 cucumber version.
5) 
```ruby
@server.stop if @server
```
Condition here needed because i don't start server and don't initialze @server in first scenario:
```ruby
Scenario: Show help information
    When I run `httparty --help`
    Then the output should contain "-f, --format [FORMAT]"
```
6) Also, you can now close another pull request by @dugancathal (https://github.com/jnunemaker/httparty/pull/311)