Enable warning option in test task
Rename unused local variable

It removes below ruby's warning.

* "assigned but unused variable"
Use parentheses for rest arguments

It removes below ruby's warning.

* "`*' interpreted as argument prefix"
Declare some instance variables via Message#initialize

It removes below ruby's warning.

* "instance variable @{ivar} not initialized"
Merge pull request #1 from kachick/improve-remove_warnings

Remove some warnings