Add --no-color cli flag

closes #72

spec/ameba/cli/cmd_spec.cr

@@ -57,6 +57,16 @@ module Ameba::Cli
         c.formatter.should eq :todo
       end
 
+      it "accepts --no-color flag" do
+        c = Cli.parse_args %w(--no-color)
+        c.colors?.should be_false
+      end
+
+      it "doesn't disable colors by default" do
+        c = Cli.parse_args %w(--all)
+        c.colors?.should be_true
+      end
+
       it "ignores --config if --gen-config flag passed" do
         c = Cli.parse_args %w(--gen-config --config my_config.yml)
         c.formatter.should eq :todo

src/ameba/cli/cmd.cr

@@ -7,7 +7,7 @@ module Ameba::Cli
 
   def run(args)
     opts = parse_args args
-    config = Config.load opts.config
+    config = Config.load opts.config, opts.colors?
     config.files = opts.files
 
     configure_formatter(config, opts)
@@ -26,6 +26,7 @@ module Ameba::Cli
     property only : Array(String)?
     property except : Array(String)?
     property? all = false
+    property? colors = true
   end
 
   def parse_args(args, opts = Opts.new)
@@ -66,6 +67,10 @@ module Ameba::Cli
         opts.formatter = :todo
         opts.config = ""
       end
+
+      parser.on("--no-color", "Disable colors") do
+        opts.colors = false
+      end
     end
 
     opts

src/ameba/config.cr

@@ -46,7 +46,8 @@ class Ameba::Config
   # config = Ameba::Config.load
   # ```
   #
-  def self.load(path = PATH)
+  def self.load(path = PATH, colors? = true)
+    Colorize.enabled = colors?
     content = File.exists?(path) ? File.read path : ""
     Config.new YAML.parse(content)
   rescue e