Fix pushbullet issue

[bobnwk]

Description:

Related issue (if applicable): fixes #

Pull request in home-assistant.github.io with documentation (if applicable): home-assistant/home-assistant.github.io#<home-assistant.github.io PR number goes here>

Example entry for configuration.yaml (if applicable):

Checklist:

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated in home-assistant.github.io

If the code communicates with devices, web services, or third-party tools:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• New dependencies have been added to the REQUIREMENTS variable (example).
• New dependencies are only imported inside functions that use them (example).
• New dependencies have been added to requirements_all.txt by running script/gen_requirements_all.py.
• New files were added to .coveragerc.

If the code does not interact with devices:

• Local tests with tox run successfully. Your PR cannot be merged unless tests pass
• Tests have been added to verify that the new code works.

[Danielhiversen]

Fix bug mentioned here: https://community.home-assistant.io/t/pushbullet-error-in-0-52/25700/5?u=danielhiversen

[firstof9]

Confirmed it resolves the error.

[bachoo786]

I am still getting the error below, I have changed the pushbullet.py file and I am still getting errors in 0.52.1

2017-09-03 22:28:51 ERROR (MainThread) [homeassistant.components.notify] Error setting up platform pushbullet
Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.4/site-packages/homeassistant/components/notify/__init__.py", line 103, in async_setup_platform
    platform.get_service, hass, p_config, discovery_info)
  File "/usr/lib/python3.4/asyncio/futures.py", line 388, in __iter__
    yield self  # This tells Task to wait for completion.
  File "/usr/lib/python3.4/asyncio/tasks.py", line 286, in _wakeup
    value = future.result()
  File "/usr/lib/python3.4/asyncio/futures.py", line 277, in result
    raise self._exception
  File "/usr/lib/python3.4/concurrent/futures/thread.py", line 54, in run
    result = self.fn(*self.args, **self.kwargs)
  File "/srv/homeassistant/lib/python3.4/site-packages/homeassistant/components/notify/pushbullet.py", line 34, in get_service
    from pushbullet import PushBullet
  File "/srv/homeassistant/lib/python3.4/site-packages/pushbullet/__init__.py", line 2, in <module>
    from .pushbullet import Pushbullet
ImportError: cannot import name 'Pushbullet'