Update Introduction.rmd

grammar
Update OO-essentials.rmd

Switched heterograph:  "right" was spelled "write"
Just spelling/punctuation
Added missing "no" to the statement about scalars.

Note that R has NO 0-dimensional, or scalar types. Individual numbers or strings, which you might think would be scalars, are actually vectors of length one.
Update Data-structures.rmd

Repetition of "type" in first answer of quiz.
Update Subsetting.rmd

not sure if this is a typo or i'm misunderstanding something..
Update Subsetting.rmd

that one is definitely a typo
Fix typoes. Closes #527
Merge pull request #526 from ajdamico/patch-2

Update Subsetting.rmd
Merge pull request #524 from freezby/patch-1

Update Data-structures.rmd
Merge pull request #523 from otepoti/patch-1

Added missing "no" to the statement about scalars.
Merge branch 'master' of github.com:SplashDance/adv-r into SplashDance-master
Merge branch 'SplashDance-master'
Merge branch 'master' of github.com:hadley/adv-r

Conflicts:
	Data-structures.rmd
Merge pull request #521 from whitwort/patch-1

Update OO-essentials.rmd
Merge pull request #519 from jvcasill/patch-1

Update Introduction.rmd
Merge pull request #525 from ajdamico/patch-1

Update Subsetting.rmd