BondSize - effectiveUpdateTime should be uint64
In BondSize, the mechanism to update the size of the bond has a grace period after which the new bond size becomes active.\\nWhen updating the bond size, the time is casted as a `uint64` and saved in a `uint128` variable.\\n```\\nuint128 effectiveUpdateTime;\\n```\\n\\n```\\nuint64 constant public WAITING\\_PERIOD = 2 days;\\n```\\n\\n```\\nself.effectiveUpdateTime = uint64(now) + WAITING\\_PERIOD;\\n```\\n\\nThere's no need to use a `uint128` to save the time if it never will take up that much space.
Change the type of the `effectiveUpdateTime` to `uint64`.\\n```\\n- uint128 effectiveUpdateTime;\\n+ uint64 effectiveUpdateTime;\\n```\\n
```\\nuint128 effectiveUpdateTime;\\n```\\n