Use container-fluid for HTML documents

Without this, as the browser is resized, the content width changes
as a step function instead of continuously.
use / separators on windows for consistency
bump version
bug fix: there might be multiple bib databases, and each bib needs its own --bibliography

see for example https://github.com/yihui/knitr/blob/master/vignettes/knitr-intro.Rmd

here I used a little trick rbind() to generate a vector that assigns --bibliography to each bib file
associate cache dir with the output format as well
use single cache directory with format-specific subdirs
Merge pull request #108 from rstudio/cache_dir

associate cache dir with the output format as well
automatically set LANG before calling pandoc on linux if it doesn't exist
Merge pull request #94 from rstudio/bugfix/container-fluid

Use container-fluid for HTML documents
Merge remote-tracking branch 'origin/master' into htmltools-refactor