Allow ALL taxed U.S. citizens the permission to vote.

As a citizen of the United States, I enjoy my freedoms and the facilities I have, and as a working citizen, I see taxes taken out of my check every time that I get paid to fund them.
I cannot, however, fully enjoy my rights as a citizen. Even though I work and pay taxes, I do not get the right to vote because I'm under 18.
When this country was founded, a main grievance of the Colonies was "No taxation without representation." And now this grievance has come up yet again.
If we're old enough to drive, make our own money, and get taxed, we're old enough to vote.
I'm open to having a test in place to prove we know enough about the government, political parties, etc. to vote.