Improve workflow to run things in parellel

[mjovanc]

I want to run tests parallel to save time and get faster feedback if something is broken instead of doing tests after each other.

I want something like:

        +----------+
        |   BUILD  |
        +----------+
             |
             V
       +------------------+
       |   UNIT TESTS     |
       +------------------+
            /       \
           /         \
          V           V
 +----------------+   +----------------+
 | UNIT TEST (sqlite) | | UNIT TEST (mysql) |
 +----------------+   +----------------+
           |               |
           +-------+-------+
                   |
                   V
          +-------------------+
          |  INTEGRATION TESTS |
          +-------------------+
              /           \
             /             \
            V               V
 +---------------------+   +---------------------+
 | INTEGRATION TEST    |   | INTEGRATION TEST    |
 |      (sqlite)      |   |      (mysql)       |
 +---------------------+   +---------------------+
             |                          
             V
         +------+
         |  DONE  |
         +--------+

[mjovanc]

Note that both integration tests needs to be passed in order for the workflow to be green.