move charm.go from testing to charm/testing
Merge remote-tracking branch 'origin/master' into 004-move-testing-charm

Conflicts:
	charm/bundle_test.go
charm: fix tests
Merge remote-tracking branch 'origin/master' into 004-move-testing-charm
state/apiserver: use charmtesting
Merge pull request #40 from rogpeppe/004-move-testing-charm

This is a prereq to pulling the charm package out of core.