Merge pull request #1 from eddelbuettel/install_foo

create addition 'install_foo' targets for more consistent interface
Merge pull request #2 from eddelbuettel/install_foo

more compact case statement
cleanup
cleanup
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