Refactor URL processing/generation into separate module

This is done to prepare for improved permalink generation
for URLs containing special characters, as proposed in
issue #782
do not force the permalink to be a dir if it ends on .html

Fixes #798.
test per-post permalinks

Add tests for setting a permalink on a post (in YAML frontmatter),
both the "old way" (generating an index.html) and with an .html ex-
tension.
delete old files that have been replaced by a directory

Fixes #417.
Replaces #1086, more logical code.
test this fix with a cucumber feature
Combined two features into one
Remove extra parentheses and swapped regex back
Updated link to the official Markuru repo as stated on Markuru homepage
Fix #1173
Merge pull request #1186 from gcapizzi/fix_command_line_params

Set short versions of --port and --host as -P and -H, respectively. Fixes #1173.
Support new private gist syntax.
Catch and print errors when MaRuKu freaks out, and exit with an error code other than 0.
Moving Quick-start guide to own section

As a new user to jekyll I wanted to get up and running as quickly as possible.

The first thing I did was jump to the docs (missing the example on the homepage - my bad) and look for the quick start guide. Since I couldn't find one I went for the 'Basic Usage' section. I ended up muddling around for about 10 minutes until I hit the home page again to see the simple - and very easy - example of how to get started.

So, in this pull request I've moved the Quick-start Guide out to it's own section so that users who really are impatient (like me) can clearly look for and jump to the quick start guide, follow the super-easy steps, and be up and running in a matter of minutes.

Interested to hear if this is thought of as being a good idea.
Merge pull request #1190 from mojombo/maruku-errors

Fail loudly on MaRuKu errors (exit code other than 0).
Update history to reflect merge of #1190. Fixes #673.
Merge pull request #1189 from mojombo/private-gist-support

Support new private gist syntax.
Update history to reflect merge of #1189. Solves #1185.
Release 1.0.3
Include instructions to upgrade to the latest version of Jekyll on 'Upgrading' page. Fixes #1194
Restructured docs a bit to accomodate new 'History' page.