add startup message
Merge pull request #138 from swirldev/startup

package startup message
Merge remote-tracking branch 'swirldev/master'
Feature: main() from command line returns to swirl main menu.
Added item to info() menu.
add brief message before returning to main menu
main.Rd generated.
fixing trivial merge conflict

Merge remote-tracking branch 'swirldev/main_feature' into main_feature

Conflicts:
	man/main.Rd
Merge pull request #142 from swirldev/main_feature

DON'T MERGE: Feature: main() from command line returns to swirl main menu.
make startup messages official
add arg to install_course_zip to help manual install
fail more gracefully on course install
make manual install more obvious
add some space
update DESCRIPTION
Fixed issue #144, Typing 0 in lesson menu causes error.
Update README.md
turn graphics off for one select.list
bug fixes and slight version increment
check challenge url for coursera submission