Expand currency test suite to fuzz test using float values

[dilatebrave]

Fix #102
I have add test_to_wei_float in test_currency_tools, but the test fail

AssertionError: assert Decimal('2.22E-15') == Decimal('2.2204460492503135E-15')
where Decimal('2.22E-15') = from_wei(2220, 'ether')
where 2220 = to_wei(2.2204460492503135e-15, 'ether')
and   Decimal('2.2204460492503135E-15') = <class 'decimal.Decimal'>('2.2204460492503135e-15')
where <class 'decimal.Decimal'> = decimal.Decimal
and   '2.2204460492503135e-15' = str(2.2204460492503135e-15)

In to_wei, should we check decimal precision of floats to throw an error instead of silently roundup the return value int(result_value)?

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[pipermerriam]

Hrm, looking at this I think it actually makes it clear that we must disallow floats or implement some kind of internal validation that rejects floats which cannot be accurately converted. I'm skeptical that we can do the later, so.. would you be up for changing this PR to instead reject float types in to_wei and from_wei and to expand/modify the existing tests to demonstrate these types are rejected.

[pipermerriam]

closing this as the removal of float support should be done in a separate PR