slog-rs logging (#171)

* added global slog instance, changed all logging macro formats to include logger instance
* adding configuration to logging, allowing for multiple log outputs
* updates to test, changes to build docs
* rustfmt
* moving logging functions into util crate

chain/src/types.rs

@@ -209,10 +209,9 @@ pub trait ChainStore: Send + Sync {
 	fn get_output_by_commit(&self, commit: &Commitment) -> Result<Output, store::Error>;
 
 	/// Gets a block_header for the given input commit
-	fn get_block_header_by_output_commit(
-		&self,
-		commit: &Commitment,
-	) -> Result<BlockHeader, store::Error>;
+	fn get_block_header_by_output_commit(&self,
+	                                     commit: &Commitment)
+	                                     -> Result<BlockHeader, store::Error>;
 
 	/// Saves the position of an output, represented by its commitment, in the
 	/// UTXO MMR. Used as an index for spending and pruning.