Adds buildable DiskLruCache source.

* Compiles against Android API 4.
* Makes the project a library project.
Assigns redundantOpCount when opening the cache.

Fixes a bug where redundantOpCount was not being tracked when
reading the journal file. This causes the journal file to grow
unless there are enough redundant ops while the cache is live.

In order to properly ensure that the cache is trimmed to size
between opening and closing the cache, redundantOpCount needs to
be counted when the cache is opened.
Reorders member entries.
Cleans up simple warnings.
Fixes ArrayIndexOutOfBoundsException.
Adds example project.
Decreases wait to 500ms.
Refactors IoUtils.deleteContents to be iterative.

deleteContents changed to be iterative from recursive. Adds a test
project and tests.
Sets minSdkVersion and targetSdkVersion on example app.
Merge pull request #2 from jonathanle/master

Adds example and test projects