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

util/src/types.rs

@@ -0,0 +1,62 @@
+// Copyright 2017 The Grin Developers
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Logging configuration types
+
+/// Log level types, as slog's don't implement serialize
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub enum LogLevel {
+	/// Critical
+	Critical,
+	/// Error
+	Error,
+	/// Warning
+	Warning,
+	/// Info
+	Info,
+	/// Debug
+	Debug,
+	/// Trace
+	Trace,
+}
+
+/// Logging config
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct LoggingConfig {
+	/// whether to log to stdout
+	pub log_to_stdout: bool,
+	/// logging level for stdout
+	pub stdout_log_level: LogLevel,
+	/// whether to log to file
+	pub log_to_file: bool,
+	/// log file level
+	pub file_log_level: LogLevel,
+	/// Log file path
+	pub log_file_path: String,
+	/// Whether to append to log or replace
+	pub log_file_append: bool,
+}
+
+impl Default for LoggingConfig {
+	fn default() -> LoggingConfig {
+		LoggingConfig {
+			log_to_stdout: true,
+			stdout_log_level: LogLevel::Debug,
+			log_to_file: false,
+			file_log_level: LogLevel::Trace,
+			log_file_path: String::from("grin.log"),
+			log_file_append: false,
+		}
+	}
+}