Exponent is now taken into account when determining value.

First off, I understand you are doing a complete rewrite of this and I only noticed that after making some modifications to the master. Instead of ignoring these updates entirely I thought I would get these updates into the master and then work on your rewrite branch going forward. Expect a couple more pull requests...

Cheers!

/ JP

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This was ignored previously and if you tried to get the value of 1.centimeter it would return 1 meter.
- Created a test for this situation.
Created a getter for @exponent value.
Updated test file to include BigDecimal for better comparison.
Updated lb to kg and kg to lb tests.