Reorganize prize priority

Single sevens are more valuable than most double fruits.
So if a user spins a grape, grape, seven, the user should receive back `playerBet * 5` not `playerBet * 2`.

In order to achieve this, the `else if (sevens == 1)` clause was moved earlier in the if/else statements.
The `else if (bells == 2)` clause was moved earlier as well because double bells are more valuable than single sevens.
So if a user spins a bell, bell, seven, the user should receive back `playerBet * 10`.

Resolves #1