Postgres: Operations, Hooks, OAuth login, Files support (#2528)

* Adds files related tests through fs-adapter with PG

* Schema deletions implementations

* Adds Hooks spec

* Fix test

* Adds support for containsAll (numbers and strings)

* Better support for deleteFields and deleteClass

* Recursive JSON update for authData

* Adds node_modules to travis cache

* Disable temporarily to make tests pass

* Adds _perishable_token support for _User class

* ignore when a table creation fails at init (table exists)

* Adds support for AddUnique and Remove

* PG 9.4 compatible functions

* Re-enable tests

* nit

* Better handling of schema creation race

.travis.yml

@@ -27,6 +27,7 @@ branches:
   - /^[0-9]+.[0-9]+.[0-9]+(-.*)?$/
 cache:
   directories:
+  - node_modules
   - "$HOME/.mongodb/versions"
 after_script:
 - bash <(curl -s https://codecov.io/bash)