Install instructions in README.md

[tngTUDOR]

I often see install instructions in the README of a repository.

• I suggest you add the install instructions from the wiki to the README.
• Also it could be interesting to add as option an install flow that would look like:

git clone https://github.com/USEPA/LCIAformatter.git
cd LCIAformatter
pip install . # or pip install -e . for devs

[bl-young]

Updated readme here d496c0e

[tngTUDOR]

openjournals/joss-reviews#3392