btcd v0.3.1-alpha

• Change default database to leveldb
  NOTE: This does mean you will have to redownload the block chain. Since we are still in alpha, we didn't feel writing a converter was worth the time as it would take away from more important issues at this stage
  
  
• Add a warning if there are multiple block chain databases of different types
• Fix issue with unexpected EOF in leveldb -- #18
• Fix issue preventing block 21066 on testnet -- btcsuite/btcchain#1
• Fix issue preventing block 96464 on testnet -- btcsuite/btcscript#1
• Optimize transaction lookups
• Correct a few cases of list removal that could result in improper cleanup of no longer needed orphans
• Add functionality to increase ulimits on non-Windows platforms
• Add support for mempool command which allows remote peers to query the transaction memory pool via the bitcoin protocol
• Clean up logging a bit
• Add a flag to disable checkpoints for developers
• Add a lot of useful debug logging such as message summaries
• Other minor bug fixes and general code cleanup