Add test coverage for the dependencies API.
user
```ruby
require 'test_helper'
require 'httpclient'

class DependenciesApiTest < Geminabox::TestCase
  test "push a gem with dependencies" do
    assert_can_push(:a, :deps => [[:b, '>= 0']])
    deps = fetch_deps("a")
    expected = [{:name=>"a", :number=>"1.0.0", :platform=>"ruby", :dependencies=>[["b", ">= 0"]]}]
    assert_equal expected, deps
  end

  test "ask about a missing gem" do
    deps = fetch_deps("nothing", "nadda", "nought")
    assert_equal [], deps
  end

  test "get dependencies for multiple gems" do
    assert_can_push(:a, :deps => [[:b, '>= 0']])
    assert_can_push(:another_gem, :deps => [[:fred, '>= 0'], [:john, '= 2.0']])
    deps = fetch_deps("a", "another_gem")
    expected = [
      {:name=>"another_gem", :number=>"1.0.0", :platform=>"ruby", :dependencies=>[["fred", ">= 0"], ["john", "= 2.0"]]},
      {:name=>"a", :number=>"1.0.0", :platform=>"ruby", :dependencies=>[["b", ">= 0"]]}
    ]
    assert_equal expected, deps
  end

  test "get dependencies for multiple versions of the same gem" do
    assert_can_push(:a, :deps => [[:b, '>= 0']])
    assert_can_push(:a, :deps => [[:b, '>= 1']], :version => "2.0.0")

    deps = fetch_deps("a")
    expected = [
      {:name=>"a", :number=>"1.0.0", :platform=>"ruby", :dependencies=>[["b", ">= 0"]]},
      {:name=>"a", :number=>"2.0.0", :platform=>"ruby", :dependencies=>[["b", ">= 1"]]}
    ]
    assert_equal expected, deps
  end

protected
  def fetch_deps(*gems)
    Marshal.load HTTPClient.new.get_content(url_for("api/v1/dependencies?gems=#{gems.join(",")}"))
  end
end
```
assistant