Simple PostgreSQL 9.4 functions to manipulate jsonb objects adapted from Matheus de Oliveira's json_manipulator.sql. https://gist.github.com/matheusoliveira/9488951 (Note: performance is not a concern for those functions)

postgresql_jsonb_crud.sql

/* 
 * derivative work of Matheus de Oliveira's json_manipulator.sql
 *   https://gist.github.com/matheusoliveira/9488951 
 *
 *  adapted to support postgresql 9.4 jsonb type
 *  no warranties or guarantees of any kind are implied or offered
 *
 *  license is as Matheus conferred it on 4/9/2015:
 *  matheusoliveira commented on Apr 9
 *    @hannes-landeholm, I'd like to take credit if you share them 
 *    (a link to this gist is more than enough), but I don't care 
 *    much about licensing, consider it public domain, modify and 
 *    use as you will.
 *       https://gist.github.com/matheusoliveira/9488951 
 */

CREATE OR REPLACE FUNCTION public.jsonb_append(data jsonb, insert_data jsonb)
RETURNS jsonb
IMMUTABLE
LANGUAGE sql
AS $$
    SELECT json_object_agg(key, value)::jsonb
    FROM (
        SELECT * FROM jsonb_each(data)
        UNION ALL
        SELECT * FROM jsonb_each(insert_data)
    ) t;
$$;

CREATE OR REPLACE FUNCTION public.jsonb_delete(data jsonb, keys text[])
RETURNS jsonb
IMMUTABLE
LANGUAGE sql
AS $$
    SELECT json_object_agg(key, value)::jsonb
    FROM (
        SELECT * FROM jsonb_each(data)
        WHERE key <> ALL(keys)
    ) t;
$$;

CREATE OR REPLACE FUNCTION public.jsonb_merge(data jsonb, merge_data jsonb)
RETURNS jsonb
IMMUTABLE
LANGUAGE sql
AS $$
    SELECT json_object_agg(key, value)::jsonb
    FROM (
        WITH to_merge AS (
            SELECT * FROM jsonb_each(merge_data)
        )
        SELECT *
        FROM jsonb_each(data)
        WHERE key NOT IN (SELECT key FROM to_merge)
        UNION ALL
        SELECT * FROM to_merge
    ) t;
$$;

CREATE OR REPLACE FUNCTION public.jsonb_update(data jsonb, update_data jsonb)
RETURNS jsonb
IMMUTABLE
LANGUAGE sql
AS $$
    SELECT json_object_agg(key, value)::jsonb
    FROM (
        WITH old_data AS (
            SELECT * FROM jsonb_each(data)
        ), to_update AS (
            SELECT * FROM jsonb_each(update_data)
            WHERE key IN (SELECT key FROM old_data)
        )
    SELECT * FROM old_data
    WHERE key NOT IN (SELECT key FROM to_update)
    UNION ALL
    SELECT * FROM to_update
) t;
$$;

CREATE OR REPLACE FUNCTION public.jsonb_lint(from_json jsonb, ntab integer DEFAULT 0)
RETURNS jsonb
LANGUAGE sql
IMMUTABLE STRICT
AS $$
SELECT (CASE substring(from_json::text FROM '(?m)^[\s]*(.)') /* Get first non-whitespace */
        WHEN '[' THEN
                (E'[\n'
                        || (SELECT string_agg(repeat(E'\t', ntab + 1) || jsonb_lint(value, ntab + 1)::text, E',\n') FROM jsonb_array_elements(from_json)) ||
                E'\n' || repeat(E'\t', ntab) || ']')
        WHEN '{' THEN
                (E'{\n'
                        || (SELECT string_agg(repeat(E'\t', ntab + 1) || to_json(key)::text || ': ' || jsonb_lint(value, ntab + 1)::text, E',\n') FROM jsonb_each(from_json)) ||
                E'\n' || repeat(E'\t', ntab) || '}')
        ELSE
                from_json::text
END)::jsonb
$$;

CREATE OR REPLACE FUNCTION public.jsonb_unlint(from_json jsonb)
RETURNS jsonb
LANGUAGE sql
IMMUTABLE STRICT
AS $$
SELECT (CASE substring(from_json::text FROM '(?m)^[\s]*(.)') /* Get first non-whitespace */
    WHEN '[' THEN
        ('['
            || (SELECT string_agg(jsonb_unlint(value)::text, ',') FROM jsonb_array_elements(from_json)) ||
        ']')
    WHEN '{' THEN
        ('{'
            || (SELECT string_agg(to_json(key)::text || ':' || jsonb_unlint(value)::text, ',') FROM jsonb_each(from_json)) ||
        '}')
    ELSE
        from_json::text
END)::jsonb
$$;

postgresql_jsonb_crud_examples.sql

postgres=# SELECT jsonb_append('{"a": 1}', '{"b": 2, "c": 3, "a": 4}');
       jsonb_append
--------------------------
 {"a": 4, "b": 2, "c": 3}
(1 row)

postgres=# SELECT jsonb_delete('{"b": 2, "c": 3, "a": 4}', '{b, c}');
 jsonb_delete
--------------
 {"a": 4}
(1 row)

postgres=# SELECT jsonb_update('{"a": 1}', '{"b": 2, "c": 3, "a": 4}');
 jsonb_update
--------------
 {"a": 4}
(1 row)

postgres=# SELECT jsonb_merge('{"a": 1}', '{"b": 2, "c": 3, "a": 4}');
       jsonb_merge
--------------------------
 {"a": 4, "b": 2, "c": 3}
(1 row)