v0.6.4 update is out

[h2]What's new in v0.6.4/h2] * New Feature: Nitro Boost ability. As you drive your Nitro builds up, once it's fully loaded you can activate it with X or Space on the keyboard. * Improved: Removed all boost areas, it's more fun to use Nitro Boosters and you can select when and where to boost. * Improved: Improved AI a lot! * Improved: When you use boost the gamepad vibrates. * Improved: Gamepad button layout is shown in UI when selecting cars. * Fixed bug: Spawn handler threw and error but it doesn't seem to have an impact on the actual gameplay. * Fixed bug: When unlocking a new car the UI was covered by a see through panel which wasn't supposed to be there. * Fixed bug: Change course no longer plays Swoosh sound effect.