(Fix) Cast to bigNumber values returned by contracts

[fernandomg]

Closes #706

In spite of what's pointed out in the bug details, this bug was caused by treating values returned by contracts as numbers and not as bigNumber.

There were values not being properly converted: weiRaised and tokensSold. And to prevent any possible issue, I also did changes to investors.

[coveralls]

Pull Request Test Coverage Report for Build 1752

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage increased (+0.02%) to 15.673%

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Totals
Change from base Build 1744:	0.02%
Covered Lines:	388
Relevant Lines:	1980

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💛 - Coveralls

[vbaranov]

@fernandomg the changes fix the issue, but maybe we can force convert input to string here

token-wizard/src/components/Common/BigNumberInput.js

Line 52 in 28b179e

const number = new BigNumber(value)

also, as @rstormsf suggested? It is not so big change but could rid of a possible headache.

[fernandomg]

@vbaranov BigNumberInputs are of type text

token-wizard/src/components/Common/BigNumberInput.js

Line 112 in 28b179e

type="text"

I can make that conversion, but will be redundant and unnecessary in this case.