Merge pull request #4 from angerhang/master

Bootstrap: Expose bind()
Merge pull request #5 from angerhang/master

HTML: Add Image
Add implicits for channel-to-widget conversions
Merge pull request #7 from angerhang/master

CachedAggregate: Add get() in consistency with Channel
Merge pull request #8 from angerhang/master

Channel: Add overloaded append()
Merge pull request #9 from angerhang/master

Channel: Fix bug in map()
CachedAggregate: Implement flush()