text: Title: Clarifications to 'Get Started!' section of documentation, based on errors encountered
  Body: ## Clarifications to the `Get Started!` section of contributing.html
  
  All: It took me a surprisingly long time to get the `pyjanitor` development environment set up on Windows 10. I have a couple of questions and an offer to add some clarifications
  
  ## Relevant Context
  
  <!-- Please put here, in bullet points, links to the relevant docs page. A few starting template points are available
  to get you started. -->
  
  - [Contributing.html](https://pyjanitor.readthedocs.io/contributing.html)
  - What follows refers to the [Get Started!](https://pyjanitor.readthedocs.io/contributing.html#get-started) section
  ### 1. Running make on Windows
  I got stuck while trying to run make. The documentation is helpful and instructed me to run:
  
       $ conda install -c defaults -c conda-forge make
  
  This worked fine. However, even though `make` was installed, I got the 'bash: make not found' error. 
  
  *Question:* How to follow up after conda installing make? Do I need to add it explicitly to $PATH? The documentation does not explain this part.
  
  After a lot of searching, I found one fix that let me proceed. It had to do copying with MinGW, 
  which has a `make` in one of the bin directories. (I can add a note in docs to this for other Windows developers who will follow. Not sure how typical this is.)
  
  Finally, got `make install` to work fine.
  
  ### 2. Running `make docs`
  
  Next, I was hit with an error saying modules were not found. (But `make install` had worked fine.) I was following the instructions verbatim, but there was no mention of activating the conda environment.
  
  Once I ran `source activate pyjanitor-dev` things worked fine when I *then* ran `make docs`
  
  If my understanding is correct, source activate is needed prior to running `make docs` 
  
  Based on my experience, I'd like to make a few very minor modifications to the 'Getting Started' section of the documentation to make it easier for future developers of pyjanitor.
  
  Please let me know if this is something that would be relevant. Also, I am not sure if my understanding of the steps is correct.
  
  Or perhaps my experience was not typical, in which case we shouldn't modify the Getting Started instructions.