Unnecessary precision loss in `_recipientBalance()`
Using `ratePerSecond()` to calculate the `_recipientBalance()` incurs an unnecessary precision loss.\\nThe current formula in `_recipientBalance()` to calculate the vested amount (balance) incurs an unnecessary precision loss, as it includes div before mul:\\n```\\nbalance = elapsedTime_ * (RATE_DECIMALS_MULTIPLIER * tokenAmount_ / duration) / RATE_DECIMALS_MULTIPLIER\\n```\\n\\nThis can be avoided and the improved formula can also save some gas.
Consdier changing to:\\n```\\nbalance = elapsedTime_ * tokenAmount_ / duration\\n```\\n
Precision loss in `_recipientBalance()`.
```\\nbalance = elapsedTime_ * (RATE_DECIMALS_MULTIPLIER * tokenAmount_ / duration) / RATE_DECIMALS_MULTIPLIER\\n```\\n