Made the injected markup configurable, added docs

Fixes #7, Micro-optimization of resulting HTML

This is a much broader fix then the one purposed in #7 by @NV.  It
allows the user to use any markup desired, thus allowing it to be
consistent with the rest of their site without having to modify Asset
Bundler itself.
moshen on GitHub sounds better... I think.
Modify Bundle.config to load configuration only once

Since more and more has crept into Bundle.config, I have modified it to
stash the loaded config into a class variable and simply return it on
subsequent calls.
Made supported_types a class variable on Bundle

This change is only to clarify the code, having all the global
configuration in one place.

Added the static method Bundle.supported_types
Added note on the compression gems and Windows

There seem to be constant compatibility problems.

Refs #6, Generates infile but no outfile
Fix asset bundler to work with liquid 2.2.2

Old versions of Liquid::Block return an array instead of a string
despite what is specified in the Tag class stubs.

This fix is ONLY to work with older versions of liquid.  Newer versions
work as expected.

Fixes #8, can't convert Array to String - error
Replace cdn configuration param with server_url

Did this because of questions around the purpose of the cdn parameter,
making it clearer what each configuration parameter does.

This commit includes config code to make sure that the cdn parameter
continues to work as expected.
Minor fixes to README.md, comma and bold

Why don't I double check this stuff the first time around?
Fix asset_bundler to work with jekyll 0.12.0
Changing the reference for creating the cache folder
Using the first item of plugins conf array or just plugin conf string
Add version reference to asset_bundler.rb
Correctly check if running in server (aka server) mode
Make serving check backwards compatible

Turns out Jekyll v1 isn't actually released yet
Bump version for release

Adds Jekyll 1.0 compatibility
Fixes #11
Fixes #12
Enabling asset_bundler dev mode when watch attribute is in conf
Reformating code
Removing old comment
Fixes #13, watch means dev mode

Though, we probably still want serving
Clean up code consistency, remove < jekyll 1 code

- Remove compatibility checks for versions of jekyll < 1
- Compare classes/types with appropriate methods
- Converted inserted tabs to 2 spaces
Bump version to v0.11 for release

- Updated docs to reflect changes