Create requirements_dev.txt file

[cbeddow]

This should be created in the main directory.

It should include the following dependencies inside it:

• pip==19.0.3
• wheel==0.33.1

Double check that those are the latest versions of pip and wheel, or add the latest version ID for Python 3.

We need to consider adding these libraries and latest version also:

• fiona
• mercantile
• mapbox-vector-tile

[Rubix982]

Should be solved by #9

[Rubix982]

Done, with the merging of #9