Default pip flags in generated README should not include "editable"

[Ian Kenney]

In the generated README, we instruct the user to install with the -e flag. This isn't really the best option by default.

cookiecutter-mdakit/{{cookiecutter.repo_name}}/README.md

Lines 41 to 45 in 457bcde

 Build this package from source: 
  
 ``` 
 pip install -e . 
 ``` 

[Lily Wang]

Ahh good point. Could you open a PR please?