Fix error triggering unrelated error (synchrony)
Fix error triggering unrelated error (synchrony)

When `@req.succeed` was called with an error reply that was never
rescued, this error would bubble back to `@req.succeed`, and be caught
by an unrelated rescue block. This rescue block would try to resume the
now dead fiber with the error it caught, resulting in a `FiberError`.

This change unwraps the `@req.succeed` and `@req.fail` calls from blocks
where errors are rescued, such that any error that they trigger will
properly bubble up the call stack (back to EventMachine).

Fixes #248.

Shopify/redis-rb,xiewenwei/redis-rb,byroot/redis-rb,redis/redis-rb,Shopify/redis-rb,YaronWittenstein/redis-rb,gallodigital/redis-rb,plribeiro3000/redis-rb,mcull/redis-rb,ckhall/redis-rb,marshall-lee/redis-rb,byroot/redis-rb,mcull/redis-rb,ckhall/redis-rb,Shopify/redis-rb,redis/redis-rb,madmax9242/redis-rb,nicolasleger/redis-rb,nicolasleger/redis-rb,YaronWittenstein/redis-rb,tanomsak/redis-rb,gallodigital/redis-rb,tsuwatch/redis-rb,RedisLabs/redis-rb,Talkdesk/redis-rb,tsuwatch/redis-rb,rranelli/redis-rb,xiewenwei/redis-rb,marshall-lee/redis-rb,ckhall/redis-rb,antirez/redis-rb,madmax9242/redis-rb,gallodigital/redis-rb,zBMNForks/redis-rb,axos88/redis-rb,teslamotors/redis-rb,byroot/redis-rb,redis/redis-rb,teslamotors/redis-rb,rranelli/redis-rb,zBMNForks/redis-rb,plribeiro3000/redis-rb,Talkdesk/redis-rb