Updated readme file to include --reinstall-packages-from#795

Merged

ljharb merged 3 commits intonvm-sh:masterfrom reybango:master

Aug 4, 2015

+17

Commits on Aug 4, 2015

Updated usage instructions to include --reinstall-packages-from syntax and example
reybango
committed
Updated to added npm to the text
reybango
committed
Updated based on feedback from @ljharb on syntax description and functionality
reybango
committed