add toml example, use yaml in help doc

Signed-off-by: Andrey Nering <andrey.nering@gmail.com>

cmd/task/task.go

@@ -15,17 +15,12 @@ task [target1 target2 ...]: Runs commands under targets like make.
 Example: 'task hello' with the following 'Taskfile.json' file will generate
 an 'output.txt' file.
 '''
-{
-  "hello": {
-    "cmds": [
-      "echo \"I am going to write a file named 'output.txt' now.\"",
-      "echo \"hello\" > output.txt"
-    ],
-    "generates": [
-      "output.txt"
-    ]
-  }
-}
+hello:
+  cmds:
+    - echo "I am going to write a file named 'output.txt' now."
+    - echo "hello" > output.txt
+  generates:
+    - output.txt
 '''
 `)
 	}

example/Taskfile.json

@@ -8,4 +8,4 @@
       "output.txt"
     ]
   }
-}
+}

example/Taskfile.toml

@@ -0,0 +1,3 @@
+[hello]
+cmds = ["echo \"I am going to write a file named 'output.txt' now.\"", "echo \"hello\" > output.txt"]
+generates = ["output.txt"]