print system information (deliberately run from R and not Rscript)
after_install -> before_script
add self-test
add tests for installation of apt and GitHub packages
add test to assert that packages aren't installed by default
install another package for testing
install binary R packages with just one apt-get install call -- again

- otherwise the logs just look horrible: https://travis-ci.org/yihui/tikzDevice/builds/13447667, lines 365-700
- runtime penalty is substantial, too
Merge pull request #55 from krlmlr/sysinfo

before running test, print system information
check pre-condition for GitHub package test
Merge pull request #57 from krlmlr/selftest

add tests for installation of apt and GitHub packages
Make a few tweaks to `.travis.yml` tests.
Make a test quieter.
Merge pull request #59 from krlmlr/binary-install-single

install binary R packages with just one apt-get install call -- again
Tweak binary name generation.
Drop a section from the sample.

[ci skip]
expose EnsureDevtools again through old command devtools_install

Reason: Running extensive integration tests (such as in tikzDevice) that are not part of R CMD check but require installation of the package

Installation can be done easily by `devtools:::install('.')`
Merge pull request #62 from krlmlr/keep-devtools

Expose EnsureDevtools again through old command devtools_install