Merge pull request #29 from yulijia/master

Avoid warning twice
update demo('flowers'): these images have been moved
cosmetic: rewrap roxygen comments and reindent code
update package URL
cosmetic
add CITATION info for JSS
all datasets are lazyloaded now (LazyData: yes), so no need to use data()
add citation in ?animation
update references: some have been moved to vistat
roxygenize
tweak description
news for version 2.2
roxygenize
add .travis.yml to enable testing on Travis CI
bump version; I think it is ready for CRAN now
do not link to rgl, since R CMD check may warn against it if it is missing
use NA (more natural here) instead of NULL
cosmetic
that is not true -- clt.ani() returns p-values
update the link to CLT demo