Ignoring of empty actions.

Heymaster\Adapters\NeonAdapter: added ignoring of empty actions, changed
error messages.
Heymaster\Adapters\BaseAdapter: added support for reporting of warnings
heymaster.phpc: changed error message, added printing of warnings
Heymaster\Adapters\NeonAdapter: added support for command syntax without
parameters

Example:

before:
  my-action:
    actions:
      complex-command: # with arguments
        arg0: 'a value'
      - simple-command # without arguments
      - second-command # without arguments

Signed-off-by: Jan Pecha <janpecha@email.cz>
readme.md: updated

Signed-off-by: Jan Pecha <janpecha@email.cz>