Merge pull request #4 from Thibauth/master

[lec3] typo fix (phantom n factor)
lecture 9
Merge branch 'master' of github.com:harvard-cs224/Scribe-Notes
fix typo lec 7
lec 7 bibliography fix
Small typo fix
lecture 10
Fix typo ( r(x) = log(s(x)) )
l_i can be zero so O(1+\sum l_i m_i) \neq O(\sum l_i m_i)
Merge pull request #5 from Keno/patch-1

Small typo fix
lec11
Merge branch 'master' of github.com:harvard-cs224/Scribe-Notes
lec 12 notes
Merge pull request #6 from yifanwu/lecture12_scribe

lec 12 notes
lec12
lec13
proper citation for dual fitting in lec10
piotr slides
added lec14
Merge pull request #7 from jchinlee/lecture14_revisions

added lec14