Release 2.0.0-alpha.0

• chore(release): publish to next tag on npm (3cfdea3)
• ci: Setup circleci 2 (f3de29a)
• doc: add example (68aeeb2)
• chore(release): use release-it for releases (a1bd73f)
• chore(lint): add and fix lint (e45981f)
• chore: remove unused code (bc16e06)
• test(bind): add document binding test (40aa4c9)
• test(unbind): test document unbind (6511f35)
• feat(unbind): manually unbind a ref (7667fe5)
• feat(refs): clear $firestoreRefs on $destroy (250a4f9)
• feat(refs): add $firestoreRefs (d7a90ee)
• test: enusre _firestoreUnbinds (e6716e1)
• feat(unbind): unsubscribe when vm is destroyed (4804381)
• chore: deep testing spec files (7ffb305)
• chore: append spec to tests (c01b78a)
• feat(bind): manual bind with $bind (8256ecb)
• chore(update dependencies): (d93915c)
• test(use custom DocumentSnapshot mock): (e7f2f31)
• chore(update ava): (0fcc6e5)
• feat(support document binding): (c1a1865)
• chore(ignore dist folder): (05980a0)
• build: add rollup build (8efe3c1)
• test(collection): fix no firestore test (a7afce3)
• test(collections): Add mock + tests for simple collections (1acd0b6)
• feat(collections): Add suport for collections (9642e47)
• chore: initial commit (f4c9678)