Add native Trampoline support for unbounded recursion
Basic docs for trampolines
Hack to make imported names safe.

This fixes a bug where imported identifiers with reserved names were
not being changed during codegen.
Move splitDots and prevent a non-exhaustive pattern match warning
Change semantics of keepWhen/dropWhen.

They no longer propagate the right Signal when the left Signal
changes.
Uncomplicate keepWhen implementation
Remove old JS dropWhen/keepWhen
Simplify Trampoline datatype.
Update trampoline docs to new interface.
Tweak runtime so it runs without a "window" object defined.
Better window workaround. Thanks @raynos
Get rid of dead code, cannot be called because of the type checker
attempt to make the documentation easier
Try to improve error messages in response to issue #479
Get rid of isClicked

It can be argued that everything should be derived from isDown and
position (the two real facts about the mouse), so maybe that is a
direction to go from here.
fix bad markdown performance
also improve the interpolation parser
don't set html if it's still the same
delay computation of the height of RawHtml