test: update string to support new version of mongodb
config: add feature flagging
config: warn when unused flags in user config
instrumentation: first pass at Express 4 tests
instrumentation: connect 3 tests
instrumentation: first pass at getting transaction name out of express4
test: turn on all feature flags during testing
deps: upgraded contuation-local-storage to 3.x

tests: removed tests for unwritten features (connect3)
news: add release notes for 1.5.1
release: published 1.5.1