Making greetings option actually allow function instead of string

In the docs it says: greetings [string|function(callback)] — default is set to JQuery Terminal Singnature. You can set it to string or function (like prompt) with callback argument which must be called with your string.

I just added the code that allowed you to use a callback.
If the command line is hidden, don't accept input.

Whenever a user types something, I use an AJAX call to get the information they need. The command line would be visible and then the data would squeeze between the command line and my last entered command. So I just hid the command line by `$('.cmd').css('visibility', 'hidden');`. Then once I get my data back, I show the command line again. Even though it was invisible, the user could still type commands. Adding this simple check makes this terminal AJAX friendly.
Fix #126
Don't call terminal::resize init, only calculate number of chars
Fix CSS empty line
Merge remote-tracking branch 'remotes/AustP/patch-1'
Merge remote-tracking branch 'remotes/AustP/patch-2'

Conflicts:
	js/jquery.terminal-src.js