Prioritize unary message over binary message over keyword message

[Minori Yamashita]

In smalltalk

receiver1 keyword: receiver2 + receiver3 unarySelector

is equivalent to
2)

receiver1 keyword: (receiver2 + (receiver3 unarySelector))

Current LittleSmallscript interprets the code 1 as
3)

((receiver1 keyword: receiver2) + receiver3) unarySelector;

[Minori Yamashita]

As a result of solving this issue, too many parenthesis are appearing in the compiled JS.

[Minori Yamashita]

Reduced some parenthesis.
Closing this issue for now.