Encouragement displays only on dirty state change

Previously encouragement would display when

1. A Save operation occurred independent of whether or not the document
was dirty
2. A Save All operation occurred and document was dirty

This unifies the behavior to display encouragement only when the file is
actually saved (the dirty state changes).
closes #13
Merge pull request #14 from Haacked/fixes-13

Encouragement displays only on dirty state change