Implement env rename command

lib/actions/environment-variables.coffee

@@ -39,3 +39,7 @@ exports.add = permissions.user (params, options) ->
 
 	resin.models.environmentVariables.create options.application, params.key, params.value, (error) ->
 		resin.errors.handle(error) if error?
+
+exports.rename = permissions.user (params, options) ->
+	resin.models.environmentVariables.update params.id, params.value, (error) ->
+		resin.errors.handle(error) if error?

lib/app.coffee

@@ -363,6 +363,17 @@ capitano.command
 	options: [ applicationOption ]
 	action: actions.env.add
 
+capitano.command
+	signature: 'env rename <id> <value>'
+	description: 'rename an environment variable'
+	help: '''
+		Use this command to rename an enviroment variable from an application.
+
+		Examples:
+			$ resin env rename 376 emacs
+	'''
+	action: actions.env.rename
+
 capitano.command
 	signature: 'env rm <id>'
 	description: 'remove an environment variable'

lib/resin/models/environment-variables.coffee

@@ -55,6 +55,29 @@ exports.create = (applicationId, name, value, callback) ->
 	.catch (error) ->
 		return callback(error)
 
+# Update an environment variable value from an application
+#
+# @param {String, Number} applicationId application id
+# @param {String} value environment variable value
+# @param {Function} callback callback(error)
+#
+# @example Update an environment variable
+#		resin.models.environmentVariables.update 317, 'vim', (error) ->
+#			throw error if error?
+#
+exports.update = (id, value, callback) ->
+	return pine.patch
+		resource: 'environment_variable'
+		id: id
+		data:
+			value: value
+
+	.then ->
+		return callback()
+
+	.catch (error) ->
+		return callback(error)
+
 # Remove environment variable
 #
 # @param {String, Number} id environment variable id