Update manual.mdown

file name error
Merge pull request #407 from dongxiong/patch-1

Update manual.mdown
fix: remove references to dropdown-list.el in Rakefile
Closes #406: correct docstring for yas-extra-modes
inhibit change hooks during (insert content)

`yas-expand-snippet' narrows to a 0 size region before doing (insert
content), this confuses cc-mode's before-change-functions that
invalidate some cached information. Binding `inhibit-modification-hooks'
to `t' prevents calling these functions.

Fixes #404.
add: test for issue #404
fix: don't use universal-argument-num-events