Update _panel2.md

shorter, playful wording, inciting action. Understanding Parliament is ok but is that all we want here?
Update _panel3.md

I found the sudden mention of laws jarring, so added the connection between them voting and changing the law. Also made it a bit shorter, and emphasised user action over simply accessing (which people are going to do anyway)
Update tests to match changes in last two commits
Merge pull request #824 from openaustralia/landing_page_words

Landing page words - panels 2 & 3