Mixed fixes

[cunei]

This pull request collects the following minor fixes:

• Reverse the parsing order of properties files. Files that come later in the list should take precedence.
• Issue a more meaningful panic message if a cycle is detected while calculating "repeatableBuilds" (supposedly impossible, but one never knows)
• minor changes to the documentation
• fix to the test in PomHelperSpec
• fix to diagnostic messages for spaces

Once this pull request is merged, we are more or less ready for a new release (it could be a 0.7.1 or 0.8.0, considering all the improvements since 0.7.0).

[jsuereth]

LGTM.

Yeah we should call it 0.8.0 I think because of binary compatibility.

[cunei]

The target/cache directories are versioned with the full version number. No binary compatibility to worry about. :) Nonetheless 0.8.0 reflects better the new features and changes. It should be out within a day or two, I'm reviewing the last few details now.