The generated test file should follow renaming and moving the source file

[michalstocki]

When we rename or move a source file that have a test file in the corresponding directory under test/spec, it's really common to forget about renaming/moving the test as well. We would like the plugin to rename/move the test automatically. The following minor issues should be considered:

• should we require a user confirmation before renaming/moving a test file?
• should we apply a rename/move backwards; should rename/move of a test results in an analogous change of a source file?