Bold face instead of italic in README
Move plug.vim in a more familiar structure
Remove filetype plugin indent on from plug.vim

I like to be clear on this kind of settings in my vimrc and not kidden in some
function call
Simplify plug#begin(...) paramether

Rename s:path -> s:normalize_path
Refactor s:add(...) function
Add notes
Rename s:rtp to s:relative_rtp and calculate one time per plug
Refactor plug#end()
Change format for 'on' command, permit range

Now load on command syntax is:

Plug 'author/plugin', { 'on': [':Command', ':AnotherCommand'] }
Plug 'author/plogin', { 'on': ':YetAnotherCommand' }
Swap check order for 'on' event

Check a 'on' command event is simpler and more common
Rename s:load_on to s:is_to_load_on
Inline to_list invocation
Comment out all the part relative to the Plugfile

In case I didn't understand well how it works
Extract utility function from s:add and change interface of s:add
Move the `git` check from plug#begin where needed

When using vim-plug constantly git will be there for sure and I don't want to
check every time vim start if git is available.
Short definition of the plugged directory
Remove control of duplicate plugs
Ignore silently if more then one option is passed
Rename variable to be more close to the domain
Extract s:parse_opts function

Now if given something else than a string or a map the option is ignore silently