Fix version placeholders

Currently:
```
"bukkitVersion":"1.8.8-R0.1-SNAPSHOT",
"version":"git-Spigot-db6de12-18fbb24 (MC: 1.8.8)"
```

Should be changed to:
```
"version":"1.8.8",
"spigotVersion":"git-Spigot-db6de12-18fbb24 (MC: 1.8.8)"
```