Merge pull request #2 from danking/master

Add workaround for math functions not defined in BigInteger
Merge pull request #3 from danking/master

Fix flonum parsing bug and add a test for it.
Merge pull request #4 from danking/master

Fix the "d1" bug and related parsing bugs
Merge pull request #5 from danking/master

Work around BigInteger not having expt
throw number-parsing errors that match racket's
add dan king to the list of contributers
Merge pull request #6 from danking/master

Fix the `big-tri` bug
Merge pull request #7 from danking/master

Fix inexact parsing and an old BigNum bug
Exact decimal numbers should parse as rationals

I've added a test to this effect.

The changes primarily consist of using `jsnums` methods rather than primitive JS
operations. These methods appropriately modify the number levels. The
`parseFloat` procedure has become more complicated because at every step we
ensure that exactness is preserved.