Release 0.3.4

[leancode]

Version bump and changelog for 0.3.4.

Two editor fixes since 0.3.3, both affecting the installed package:

• Pasting indented text no longer produces a staircase (Insert pasted text literally instead of as keystrokes #6). Suplemon enables bracketed paste mode and inserts the payload literally, so auto-indent does not compound and tabs stay tabs.
• Undo no longer steps back past the last edit (Keep the undo state in step with a run of typing #7). A typing run was only recorded as its first keystroke, so KEEP + enter + undo left K.

Also folds in the installer and uninstaller changes from #5, which were sitting unreleased. Those affect repository and curl | sh installs only and took effect when merged; they are listed for completeness.

The two Unreleased changelog sections have been merged into one 0.3.4 entry.