Fix find expression for looking up .Rcheck

- use quoting
- limit depth
Merge pull request #126 from krlmlr/patch-1

Fix find expression for looking up .Rcheck
Bioc deps from package description.
Merge pull request #119 from siddharthab/master

Bioconductor dependencies from package description
Bioc devtools fix and indent
Merge pull request #130 from siddharthab/master

Bioc devtools fix and indent
Update tests.

A recent devtools update removed the support for bare repo names that
defaulted to `hadley/`; tests need updated to match.
Add support for installing pandoc in travis.

This adds code to optionally install `pandoc` in the travis worker, controlled
by the new environment variable `BOOTSTRAP_PANDOC`. The installed executable
is available in `${HOME}/opt/pandoc`, which is where `rmarkdown` will look for
it by default.

Works on mac and linux.
Cleanup create-osx.sh.
Merge remote-tracking branch 'craigcitro/master' into 74-warn

Conflicts:
	scripts/travis-tool.sh
install errors are only checked if the environment variable VERIFY_INSTALL_ERRORS is nonempty