Merge branch 'master' into stable

# Conflicts:
#	package.json
#	src/flux/stores/thread-counts-store.coffee
#	src/flux/tasks/task.coffee

log(sync-state): Send `Account State Delta` to mixpanel

fix(build): Remove duplicated code in SendDraftTask

Merge branch 'master' into stable

fix(account): notify if we have bad accounts

bump(version): 0.4.5 patch release

fix(system-start): Do not continue when checkAvailability returns false

fix(contributing): Mention syncEngine.APIRoot

bump(version): 0.3.43 and changelog

fix(zoom): Only set zoom to valid numeric values