#18 Option to eliminate hidden syncs

[Daniel Kunkle]

Currently, a Roomy data structure is synced in two ways: 1) when a user call sync on it; 2) when disk space limits are reached and updates need to be synced to free space. So, for example, if user is mapping over an array and sending delayed updates to the same array, some updates may occur in the middle of the map (causing problems in some applications). Users can prevent this by having a secondary array to hold the updates temporarily, but this doubles the cost. If hidden syncs are eliminated, this secondary array can be avoided (but an error will occur when disk space is exhausted).