Merge branch 'release/2.4.1' into dev
Explicitly set timezone to UTC for tests
Extract cache interface

Refactoring to allow for alternative cache implementations. Includes
implementations for the default noop (i.e. un-cached) behavior and a
filesystem-based cache whose configuration is consistent with the
existing Mustache_Engine constructor.

Includes updated and new tests.
Fix build - explicit config key check
Cleanup cache initialization from options
Restore original eval vs. require class loading

Pushing the responsibility of class loading onto the `Mustache_Cache`
implementation and changing the semantics of get/put to load/cache.
Restore logging for cache operations

`AbstractCache` exposes the ability to set a logger. Default behavior
automatically passes the logger reference down to the cache, unless a
specific cache instance was provided.
Invalid documentation
Use existing temp directory for test
Use class name as cache key
Set logger for cache if not explicitly set
Fix broken build
Revert timezone edit
Add copyright/license header
Docs
Fix docblock
Merge pull request #166 from amitsnyderman/master

Extract cache interface
Bump copyright dates.
Clean up comments, standardize whitespace.
Add a failing test for #167

Multiple levels of nested partials are only indented to the level of the first partial.