exponents working. Squashed commits.

commit 0e56a88619ba7901f70e5a44e75675b900abb40f
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 14:56:05 2013 +1100

    remove old fmt.Prints

commit 786da53b228d6a43d1111bc8f1df7942533087cc
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 14:55:15 2013 +1100

    exponent now handled, tests

commit e205ea2af57e3dce28c553f5cb3f4481d559a124
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 14:08:10 2013 +1100

    rename test vars to 'testsFoo'; tests to TestFoo

commit 3aefff6274c24164ca082efdc73d40c7a28e8a98
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 14:04:52 2013 +1100

    done - bigrat/bigint helper functions and tests

commit 9cb94c9785c2c99f47de1364f1782a177fbc912f
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 13:49:26 2013 +1100

    testsFloatToBigrat

commit 5a8e190c1ea9903b1153977fedce80fc6e0099ac
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 13:22:06 2013 +1100

    wip testing - testBigratToFloat()

commit 53b667fe3e917c7f1ce07333c12919ccd820ffea
Author: Sonia Hamilton <sonia@snowfrog.net>
Date:   Fri Feb 22 12:48:21 2013 +1100

    wip - bigrat/bigint helper functions and tests