Would be nice to be able to customize the accounts of the testrpc node

[facuspagnuolo]

• I've asked for help in the Truffle Gitter before filing this issue.

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Issue

Testrpc develop and testing nodes define hardcoded accounts addresses and balances

Steps to Reproduce

See lines https://github.com/trufflesuite/truffle-core/blob/develop/lib/commands/develop.js#L51-L66

Expected Behavior

Testrpc accounts should be customizable as in ethereumjs-testrpc

Environment

• Truffle version: Truffle 4.0.5
• Ethereum client: Truffle