While `delete rocks_ptr` is a deterministic operation in C++, the Python analogue `del rocks_handle` is not – disposal and finalization of the Rocks database are entirely dependent on the Python garbage collector (q.v. the `python-rocksdb` tests themselves, which call `gc.collect()` after `del rocks_handle` to attempt to force the destructor to run). This change exposes a method to trigger the destruction of the underlying Rocks database pointer (deterministic!) through the Python Rocks handle; existing code will not need to be changed, as the Python object destructor (non-deterministic!) will now call this method.

This is the second revision of this PR – it resolves the first revision, #39.

Add support for Column Families in a runtime safe way.
Add unittests to test functionality
Insure all unittests are passing.
Cleaned up unittests to not use a fixed directory in tmp, but use tempfile

Merge options source_compaction_factor, max_grandparent_overlap_bytes and expanded_compaction_factor into max_compaction_bytes

(cherry picked from commit c6e4014136aa3d81ecd4288150b3eefca9849b0b)

See https://github.com/facebook/rocksdb/wiki/Prefix-Seek-API-Changes