Issue #75: wired CacheLoader where applicable.
Issue #75: corrected method signatures to include CacheLoader/CacheWriter exceptions where applicable.
Issue #75: split fix for OnHeapStore.bulkComputeIfAbsent() from main commit.
Merge pull request #121 from vfunshteyn/issue-75

Issue #75: wired CacheLoader where applicable.
Added some API example, both in code and in README.adoc