Initial move away from skiplist.
Code Review: Initial arena size name.
Code Review: Avenues for future improvemnet noted.
Code Review: Extend lock scope for appending.
Code Review: Extend lock.
Code Review: Fix to-disk queue infinite growth.

We discovered a bug while manually testing this branch on a live
instance, whereby the to-disk queue was never actually dumped to
disk.
Instruct ``make binary`` to build binary file.
Merge pull request #265 from prometheus/feature/memory-arena-simplification

Move In-Memory Arena Away from Skiplist