title: context is unavailable in python behave
body: <p>I am starting with Python behave and got stuck when trying to access context - it's not available. Here is my code:</p>
  
  <p>Here is the Feature file:</p>
  
  <pre><code>Feature: Company staff inventory
      Scenario: count company staff
              Given a set of employees:
                      | name | dept |
                      | Paul | IT   |
                      | Mary | IT   |
                      | Pete | Dev  |
  
      When we count the number of employees in each department
      Then we will find two people in IT
      And we will find one employee in Dev
  </code></pre>
  
  <p>Here is the Steps file:</p>
  
  <pre><code>from behave import *
  @given('a set of employees')
  def step_impl(context):
          assert context is True
  @when('we count the number of employees in each department')
  def step_impl(context):
          context.res = dict()
          for row in context.table:
                  for k, v in row:
                          if k not in context.res:
                                  context.res[k] = 1
                          else:
                                  context.res[k] += 1
  @then('we will find two people in IT')
  def step_impl(context):
          assert context.res['IT'] == 2
  @then('we will find one employee in Dev')
  def step_impl(context):
          assert context.res['Dev'] == 1
  </code></pre>
  
  <p>Here's the Traceback:</p>
  
  <pre><code>      Traceback (most recent call last):
          File "/home/kseniyab/Documents/broadsign_code/spikes/BDD_Gherkin/behave/src/py3behave/lib/python3.4/site-packages/behave/model.py", line 1456, in run
            match.run(runner.context)
          File "/home/kseniyab/Documents/broadsign_code/spikes/BDD_Gherkin/behave/src/py3behave/lib/python3.4/site-packages/behave/model.py", line 1903, in run
            self.func(context, *args, **kwargs)
          File "steps/count_staff.py", line 5, in step_impl
            assert context is True
        AssertionError
  </code></pre>