Changed EntityLiving to EntityPlayer/EntityMob

Defined the EntityLiving check to EntityPlayer or EntityMob checks. This
means neutral mobs are not effected by Sewage, Sludge, or the Sludge
Boiler. This lowers the chance of "Ticking Entity" crashes.
Code Cleanup

Removed the extra import as it wasn't needed in the file.
Merge pull request #113 from Yoshi667/master

Defined EntityLiving to affect only EntityPlayer and EntityMob