chore(tests): Remove 'new Symbol' call to reduce dart2js memory usage
docs(VmTurnZone): Fix some messed up markdown.

Closes #968
feat(compiler): bind- syntax

Adds support for bind- syntax which allows directive users to
give an expression for any mapping.

For #650
Closes #957
hack(travis): Increase dart2js' heap size
chore(tests): Remove a ddescribe
feat(LRUCache): Support zero-length caches
perf(compiler): 31%. Cache CSS in Style elements.

In a benchmark, I saw a 31% speedup while creating components which include
unminified Bootstrap (125K) as a cssUrl.
fix(travis): Curl should follow redirects when fetching scripts
feat(VmTurnZone): VmTurnZone can handle scheduling microtasks.

To customize how VmTurnZone handles microtasks assign a function to
VmTurnZone.onScheduleMicrotask. This method will then be used whenever
a microtask is scheduled instead of the default implementation.

Closes #976