🔖 bump version 0.3.0 -> 0.4.0

[joshuadavidthomas]

• 8a26063: correct items template context and add notes about permissions
• a567df0: further clarify the items variable in template
• 27572da: adjust nav template examples
• cf7312f: update docs with major overhaul (update docs with major overhaul #38)
• d6895e9: add get_context_data and render methods to Nav (add get_context_data and render methods to Nav #39)