title: adding dependencies to a conda environment yaml file
body: <p>I have a process to setup an initial project whereby I create a standardised conda environment based on a yaml file. </p>
  
  <p><code>conda env create -f environment.yaml</code></p>
  
  <p>The yaml file looks something like this</p>
  
  <pre><code>name: testA
  channels:
  - conda-forge
  - defaults
  - anaconda
  dependencies:
  - python=3.6.3=1
  - yaml=0.1.7=0 
  - connexion=1.1.10=py36_0
  - setuptools=38.4.0=py36_0
  - pymongo=3.4.0=py36_0
  - gunicorn=19.8.1=py36_0
  - flask-cors=3.0.6=py36_0
  </code></pre>
  
  <p>As the project progresses a user might add another library</p>
  
  <p><code>conda install scikit-learn</code></p>
  
  <p><strong>Is it possible to append the updated conda environment to original environment.yaml ???</strong> - I know I can overwrite with </p>
  
  <p><code>conda env export &gt; environment.yaml</code> </p>