We remember each cache entry that was read or written during the
current jsduck run.  All others get deleted.  This ensures the .cache
directory doesn't grow over time.

Refs #446

By default the caching is disabled.  When turned on with --cache,
the caching dir will be <output-dir>/.cache/ unless overridden
with --cache-dir option.

Previously the whole output dir got cleaned up, but now it can
contain a .cache dir, which we'll want to preserve.  So I created
OutputDir class to take care of output directory cleanup in a way
that preserves the .cache/ directory inside it.

Refs #446

At the moment the cache is just saved to .cache/ in current dir.

The parsed data is serialized into binary format using Marshal,
which correctly preserves all the data types and is additionally
really fast.

Refs #446

Refs #444

Only data properties can have the writable flag, accessor properties
can't.

Fixes #444

Force RKellyAdapter spec source to ASCII encoding.

But only when documented with a doc-comment.  Completely ignore
getters/setters when auto-detecting class members.

Fixes #441

Make the RKellyAdapter correctly adapt the getters/setters into
properties of "get" and "set" kind.

Fixes #436

This way when an actual error happens, we don't catch it with the
generic 'rescue Exception => e' block.

Create four warning classes to handle a particular set of warnings:

- Warning::Basic -- the usual warnings :tag, :link, :global, ...
- Warning::Nodoc -- the :nodoc warning type together with its
  parameters.
- Warnings::Deprecated -- the old :no_doc* warnings which delegate to
  the new :nodoc warning.
- Warning::All -- composite warning that allows enabling/disabling all
  warning types together.

Then inside Warning::Registry delegate #set and #enabled? calls to these
warnings.

The new nodoc takes parameters, but at the moment the parsing of
more than one parameter doesn't work yet.

Perform missing docs reporting in separate class.

Test the warnings system through the Warnings class instead.
Switch Logger class back to the old system of including Util::Singleton.

Make the Logger testable by defining a LoggerCls and instantiating
it as global Logger - allowing us to instantiate the LoggerCls
separately in tests.

Test the enabling/disabling of warnings.

To avoid the no_doc_param warning.

Fixes #435

Fixes #429

Something goes wrong when we execute this BOM-stripping code in
Ruby 1.8 which has encodings support.  Didn't care to digg into this,
and so I'm just limiting this fix to Ruby 1.8 where it's actually
needed.

An improvement over the previous fix by Brian Moeskau.
Saving on the horizontal space by removing the left margings
altogether.

Cosmetic margin fix for categories page

When the browser is narrow the floated columns all align left but with different margins. They should all have the same left margin so it looks consistent at any width.

When ever a method-call is detected inside a method, this results
in :fires field being created with possibly zero elements in it -
but the #to_html of Tag::Fires didn't account for it.

Fixes #428

Fixes #427

These come up fairly often. Better to have these built in.

Fix old links and simplify the Usage section - pointing people to
the new Usage guide in wiki for more.

Updated Rally AppSDK link

I work for Rally Software and noticed the link was outdated. I've updated the link to a non-redirect link and updated to the latest App SDK release.

Allowing to exclude some of the input files.
Comes in handy for Windows users especially.

Fixes #216

Adapt similar styling to Wikipedia.

Fixes #424

This fixes JSDuck crash when keywords used as property names.