Make auth.parseCredentials async

lib/auth/auth.coffee

@@ -27,13 +27,13 @@ exports.getToken = token.getToken
 # like that to invalidate the token on the server?
 exports.logout = token.clearToken
 
-exports.parseCredentials = (credentials) ->
+exports.parseCredentials = (credentials, callback) ->
 	result = credentials.split(':')
 
 	if result.length isnt 2
-		throw new Error('Invalid credentials. The expected input is username:password.')
+		error = new Error('Invalid credentials. The expected input is username:password.')
+		return callback?(error)
 
-	return {
+	callback? null,
 		username: _.first(result)
 		password: _.last(result)
-	}

lib/auth/auth.spec.coffee

@@ -175,18 +175,21 @@ describe 'Auth:', ->
 				username = 'johndoe'
 				password = 'mysecret'
 
-			it 'should parse the credentials correctly', ->
-				parsedCredentials = auth.parseCredentials("#{username}:#{password}")
-				expect(parsedCredentials.username).to.equal(username)
-				expect(parsedCredentials.password).to.equal(password)
+			it 'should parse the credentials correctly', (done) ->
+				auth.parseCredentials "#{username}:#{password}", (error, credentials) ->
+					expect(error).to.not.exist
+					expect(credentials.username).to.equal(username)
+					expect(credentials.password).to.equal(password)
+					done()
 
-			it 'should throw an error if it has two or more colons', ->
-				parseFunction = _.partial(auth.parseCredentials, "#{username}:#{password}:#{username}")
-				expect(parseFunction).to.throw(Error)
+			it 'should throw an error if it has two or more colons', (done) ->
+				auth.parseCredentials "#{username}:#{password}:#{username}", (error, credentials) ->
+					expect(error).to.be.an.instanceof(Error)
+					expect(credentials).to.not.exist
+					done()
 
-				parseFunction = _.partial(auth.parseCredentials, "#{username}:#{password}:#{username}:#{password}")
-				expect(parseFunction).to.throw(Error)
-
-			it 'should throw an error if only the username is passed', ->
-				parseFunction = _.partial(auth.parseCredentials, username)
-				expect(parseFunction).to.throw(Error)
+			it 'should throw an error if only the username is passed', (done) ->
+				auth.parseCredentials username, (error, credentials) ->
+					expect(error).to.be.an.instanceof(Error)
+					expect(credentials).to.not.exist
+					done()