Implement for loops in the frontend

[rwy7]

There were some other issues with compiling JMP in the jit, and compiling update-assignment expressions in the JS FE, which I fixed. I also added two small for-loop tests.

[coveralls]

Pull Request Test Coverage Report for Build 415

• 0 of 0 (NaN%) changed or added relevant lines in 0 files are covered.
• No unchanged relevant lines lost coverage.
• Overall coverage decreased (-0.009%) to 74.598%

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Totals
Change from base Build 414:	-0.009%
Covered Lines:	2182
Relevant Lines:	2925

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💛 - Coveralls

[youngar]

Another broken call to handle().

    // Iterate expressions array
    this.handleSequenceExpression = function (func, sequence) {
        var expressions = sequence.expressions;
        var droplast = !decl.isParameter;

        for (expression in sequence.expressions.slice(0, -1)) {
            this.handle(func, expression);
            func.instructions.push(new Instruction("DROP"));
        }

        var last = sequence.expressions.slice(-1)[0];
        this.handle(last);

        if (!sequence.isParameter) {
            func.instructions.push(new Instruction("DROP"));
        }
    };

[rwy7]

I'll open an issue for the second busted handle and deal with it later, cool?

[youngar]

@rwy0717 Sounds good, we can fix that later.

Unrelated question: do we want the coveralls check failing if we reduce test coverage?

[rwy7]

I was thinking about the same thing. Really, it's up to us to decide how to interpret the results. The threshold is configurable. I thought it was a little silly that it complains about a 0.009 % reduction in coverage, so I upped the threshold to 1%. I also disabled the comment--which I'm open to reenabling.