Added limit for days in the future to convert

[timcosta]

I added a future conversion limit to the settings, such that you may set a variable similar to allowFuture that will cause timeago to convert future timestamps up to that many days away to words, otherwise it will print a date string.

For example,

    $.timeago.settings.allowFuture = true
    $.timeago.settings.daysInFuture = 3
    $("time.timeago").timeago()

will convert any dates past three days in the future to a full date string. Today is April 23rd, so for April 27th this would print "Saturday, April 27, 2013" instead of "4 days from now".

[rmm5t]

This PR has a bunch of regressions in it. It looks like it was based on an old version of timeago.

[rmm5t]

This was added as part of PR #129 and v1.2.0