sl-date-range-picker: "endDateValue" cannot be less than than the "startDateValue"

[juwara0]

Provide a fix for "endDateValue" is allowed to be less than the "startDateValue" and then verify the fix by turning the skipped test below back on.

This test fails: test( '"endDateValue" cannot be less than "startDateValue"', function( assert ) {

this.render( hbs`
    {{sl-date-range-picker
        startDateValue="09/25/2015"
        endDateValue="09/20/2015"
    }}
` );

assert.notEqual(
    this.$( '>:first-child' ).find( '.sl-daterange-end-date' ).find( 'input' ).val(),
    '09/20/2015',
    'The "endDateValue" is not more than the "startDateValue"'
);

});

[Yogeswar]

I'm working on this. addressed by #870 (will cause merge conflicts otherwise)

[SpikedKira]

Should be resolved by #1458