Readme: remove old developer docs saying to run grunt before a PR
Readme: remove old developer docs saying to run grunt before a PR

This is hard when we have many PRs open and often get left with a bunch of merge conflicts.
snide/sphinx_rtd_theme,mitya57/sphinx_rtd_theme,mitya57/sphinx_rtd_theme,snide/sphinx_rtd_theme,mitya57/sphinx_rtd_theme,mitya57/sphinx_rtd_theme,snide/sphinx_rtd_theme,snide/sphinx_rtd_theme