Don't panic in filter divided_by on division by zero

[jamslinger]

Checklist

• I have read the contribution guidelines.
• make test passes.
• make lint passes.
• New and changed code is covered by tests.
• Performance improvements include benchmarks.
• Changes match the documented (not just the implemented) behavior of Shopify.

[jamslinger]

fixes #96

[danog]

Please implement this by actually checking the value of the denominator

[jamslinger]

Please implement this by actually checking the value of the denominator

Yes that makes sense.

• Also found and fixed another bug where type assertion was used on potentially incompatible types, e.g.:

case int, int16, int32, int64: // any non-int type would cause `q.(int)` to panic. 
			return int(a) / q.(int)

• Also extended the possible divisor types with uintX types that are convertible into int64.
• Also return an error on any invalid divisor type, this matches the behavior of Shopify liquid that returns an error when e.g. trying something like {{ 40 | divided_by: 's' }}. However, I'd like to hear your opinion on this because it might affect existing code.

[danog]

Thanks, looks all good, especially since it matches shopify behavior.