Month off by +1 when converting to Ethiopic date

[m3hari]

Today is
2017-04-30 g.c
2009-08-22 e.c

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When converting to Ethiopic calendar, the month is off by +1. Here is a snippet to reproduce the issue.

var today  = new Ken(new Date());
today.toEC().toString();

returns "2009-09-22"

[miqe]

Thanks, that only happened when using Date Object as ken input.
Fixed with #13