AzureML Provider : __init__() missing 1 required positional argument: 'compute_target'

**What happened**:
I installed dask-cloudprovider using pip within a conda environment which already have azure related dependencies available.

$ pip install dask-cloudprovider

And was trying to execute, the code from the [documentation](https://cloudprovider.dask.org/en/latest/#create-cluster).

```
amlcluster = AzureMLCluster(
# required
ws,
# optional
vm_size="STANDARD_DS13_V2", # Azure VM size for the Compute Target
datastores=ws.datastores.values(), # Azure ML Datastores to mount on the headnode
environment_definition=ws.environments['AzureML-Dask-CPU'], # Azure ML Environment to run on the cluster
initial_node_count=2, # number of nodes to start
scheduler_idle_timeout=7200 # scheduler idle timeout in seconds
)
```
It resulted in the following error:

> Exception ignored in:
> Traceback (most recent call last):
> File "/anaconda/envs/azureml_custom_py37/lib/python3.7/site-packages/distributed/deploy/cluster.py", line 93, in __del__
> if self.status != "closed":
> AttributeError: 'AzureMLCluster' object has no attribute 'status'
> ------------------------------#
> TypeError Traceback (most recent call last)
> in
> 4 environment_definition=ws.environments['AzureML-Dask-CPU'],
> 5 initial_node_count=2,
> ----> 6 scheduler_idle_timeout=7200
> 7 )
>
> TypeError: __init__() missing 1 required positional argument: 'compute_target'

On checking the code in the conda environment, I realized that the pip package doesn't include latest code in master.

In fact pypi still points to the code committed until 25th June.

**Environment**:
$ conda list | grep dask
dask 2.20.0 py_0
dask-cloudprovider 0.3.0
dask-core 2.20.0 py_0
dask-glm 0.2.0 py_1 conda-forge
dask-ml 1.6.0 py_0 conda-forge
dask-xgboost 0.1.10

$conda list | grep azure
azureml-automl-core 1.10.0.post1
azureml-core 1.10.0.post1
azureml-dataprep 1.10.1
azureml-dataprep-native 14.2.1
azureml-dataset-runtime 1.10.0
azureml-pipeline 1.10.0
azureml-pipeline-core 1.10.0
azureml-pipeline-steps 1.10.0
azureml-sdk 1.10.0
azureml-telemetry 1.10.0
azureml-train 1.10.0
azureml-train-automl-client 1.10.0
azureml-train-core 1.10.0
azureml-train-restclients-hyperdrive 1.10.0

$conda list | grep distributed
distributed 2.20.0 py37_0