Remove unused timer that is incompatible w/ Firefox

fixes #2033
Merge async.series operations without an async mode with those that do.

Some intermediate steps in async.series sequences always completed
synchronously and didn't actually need async support. Sequences were
arranged that way for clarity, but having unnecessary steps in a
series sequence is expensive on the stack.

These steps have been merged down into the following async step, or
merged into the completion function when they were at the end of
the sequence.

References #2035.
Collapse async.series sequences of length 1. References #2035.
Ensure async breaks occur before and after each createChild().

Keeps the stack from growing from node to node while createChild()
recursively traverses a component. The break at the beginning protects
the way down, and the break at the end protects the way up.

References #2035.
Don't suspend the queue when `createChild` doesn't have a callback.

References #2035.
Add stack depth tests. References #2035.
Updates for CHANGELOG.md to 0.6.10-RC2. Resolves issues with Firefox 21.