Correct grammatical errors. Props Jen Mylo

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7/trunk@1030006 b8457f37-d9ea-0310-8a92-e5e31aec5664
Update POT and Japanese translation.

git-svn-id: https://plugins.svn.wordpress.org/contact-form-7/trunk@1030013 b8457f37-d9ea-0310-8a92-e5e31aec5664