Revert "fix vagrant-1.5.x error"

This reverts commit 0fd5e2f76e81126e3890b3cd96ddc58a01c52a61.
fix vagrant-1.5 error and keep 1.4 running

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
simplify readme for migration

Signed-off-by: Hiroshi Miura <miurahr@linux.com>
Merge pull request #196 from miurahr/readme_simplify_migration

simplify readme for migration