Add guards

Cf winzou/state-machine#25 and #27 for more details.

Symfony 3 compatibility

add Symfony 3 support

* add Symfony 3 support

* fix php version

Update state-machine lib

cf. https://github.com/winzou/state-machine/releases/tag/0.2

v0.2.1: Fix callback args configuration merging

When the configuration for a callback args is split in multiple config files, we don't merge the arguments anymore. Only the last define args node is kept. Previous behavior was to add an new argument instead of overriding it, it was not the right way.

v0.2: Add ability to sort callbacks

• Add ability to sort callbacks thanks to a priority index in the callbacks config
• Fix the state disabling feature which was broken.

No BC break.

v0.1.3: Fix error when callable contains object

Fix error when callable contains object

v0.1.2

Fix configuration

v0.1.1

Add keyword

First release

v0.1

Fix autoload to psr4