Edited the "keeping passwords safe" section. Mostly just cleaned up to make things clearer and more understandable, but also reviewed and changed the info to stress password length as the most important factor when choosing a new password.
Edited 'keeping passwords safe' for brevity and clarity
Edited 'Minimizing damage' for brevity and clarity
Edited 'physical protection' section for clarity and brevity'
Edited sentence based password section for clarity and brevity
Edited password manager section for clairty and brevity
Re-ordered sections in order of importance and to make things flow
Removed redundant section on firefox passwords (with reference to non…
… existent chapter)
Edited caveat section to remove redundant info and make it clearer
Fixed spelling mistake
Edited the password length section for brevity and clarity
Stressing password length over special characters and and numbers
Thanks for the pull request @DanielKinsman.
I'll merge the request, though next time please try to squash commits together if they pertain to the same changes.