bug fixes and slight version increment
check challenge url for coursera submission
increment version slightly
purged snapshots using a lightweight substitute; still testing, but no more freezes or lags on my dev machine
Merge branch 'master' into fix_snapshot
bug fixes
Restored a line which was inadvertantly deleted.
Fixed some problems with lesson initialization.
Fixed failure to track variables created by side effects, e.g., sourcing a figure file. Requires that all variables created by side effects in the lesson must be "declared" in initLesson.R if they should be tracked.
Fixed incompatibility with custom tests in certain lessons. Code may be OK now, but don't count on it.
Fixed oversight in answer tests.
minor change
Failure to install course should now be properly indicated
possible fix to "play" bug.
incremented to version 2.2.8; added news item
Merge pull request #155 from swirldev/proper-messaging

Failure to install course should now be properly indicated
Merge branch 'master' into fix_snapshot
add item to NEWS