Merge pull request #85 from eddelbuettel/master

More standard install_* command names added
change self-test to use new functions
install_github uses new syntax which allows specifying multiple packages to be installed
remove GithubPackage function
more informative error message if test fails due to warnings
Merge pull request #87 from krlmlr/install_foo

install_github uses new syntax which allows specifying multiple packages to be installed
Merge pull request #89 from krlmlr/newbie

more informative error message if test fails due to warnings
Simplify Retry, and give up after a few retries.
Fix some bad bash syntax.
replace all instances of "$*" with "$@", use "$@" instead of $* where appropriate

Fixes #86.
Switch exit for return in retry.
Merge pull request #90 from craigcitro/new_retry

Simplify Retry, and give up after a few retries.
Merge pull request #91 from krlmlr/86-dollar-at

replace all instances of "$*" with "$@", use "$@" instead of $* where appropriate
Skip installing devtools from github by default.

Fixes #88.
Drop some extra lines from `sample.travis.yml`.

[ci skip]
Inspired by the conversation in #71.
Force `install_deps` to fail when package installation fails.

Fixes #74.
Grab a single tarball to test.

Fixes #73.
Merge branch 'source_package'
Fix a missing parens.
Undo the change to warn on install_deps failure.

Reopen #74.