[remind] Filter empty strings from the message

This fixes a problem with the .in command where not all of the arguments for the
duration get applied.
[Version]Don't PM admins when outdated, only the owner.
[web, url] Move header-based encoding detection to web.get

url.py did this really good thing where it would look for the encoding in the
HTTP headers and use them to .decode() the string returned from web.get.

web.get() gained (not too long ago) the ability to decode text itself, but it
was doing it to utf8 by default.

So instead of hardcoding utf8 in web.get, I moved that detection functionality
from url to web, so now all modules using web.get will be able to enjoy it.
[uptime] Adds a rudimentary uptime module which tells how long the
bot is running.
Merge pull request #589 from xZise/uptime-module

Adds a rudimentary uptime module
[Clock]Display timeformat correctly when informing of the net format.
Fixes #585
[Clock] Display the new format, instead of the previous one.
[core] Make message splitting work with unicode strings too
[rss] Remove annoying, useless warning when you have no RSS feeds configured
add astronomical units, and define mile more precise
Merge pull request #591 from warddr/astronomic

add astronomical units, and define mile more precise
multi-line help

	.help will now display multi-line docstrings as several
	messages, one for each line, instead of concatenating them into
	a single long one.
	Those that consist of more than a certain number of lines
	(including the example for commands that have one) will be
	PRIVMSG'd to the asker instead of being posted into a channel.
	This number (3 by default) is configurable via the [help]/threshold attribute.
De-globalized threshold variable
Merge pull request #590 from flashcactus/help_fix

[help][core] Multi-line help
pyenchant is now in pip, the refered bug report has been closed
[calc] Add tests for potential problems with the calc module.

- Added as a separate commit to confirm that the problem with .c 0.9*10
  exists and is fixed.
[calc] Fix .calc for expressions where left operand is float.

- Typo in the if-expression caused the fact that input operands are not int
  to be ignored.
[calc] Fix left operand being float for pow expressions.
[web] Fix entity() under Python 3
[web, url] Better IDN support

* Move IDN helper methods to willie.web for easier access from modules
* Make willie.web methods IDN aware
* Python 3 fixes for the IDN support