Implement Glob.matchAsPrefix()

This also allows matchesFull() to be used with Glob patterns.
Add center to quiver.strings
Fix type annotation in multimap.dart; add more meaningful types in the test so bugs like that are caught in checked mode
added missing implementation for Queue
Merge pull request #81 from yjbanov/multimap-clear-bug

Fix type annotations in multimap.dart and tests
Add Glob.matchAsPrefix() to glob test.
Merge pull request #73 from seaneagan/master

Add quiver.streams with enumerate method
Merge pull request #82 from kevmoo/fixed_queue

added missing implementation for Queue
Pad extra char on right instead of left per ruby
Add quiver.streams.concat
Fix HashBiMap to match Map<K, V> spec
Shorthand syntax for putIfAbsent
Make createTimer assignable to CreateTimer and add tests
Improve docs
Remove expectAsync usage
Add duration unit constants to quiver.time
First-stab at AVL tree set.
Reviewer comments
More cleanup.
Add .from() -> Iterator<V>