Map get takes a Tk, not an int
Merge pull request #167 from ClaudiuC/mapfix

Map get takes a Tk, not an int
Clarify async warning just a bit

Fixes #164
Fix Nullable example to actually make sense.

Fixes #134
"Hi" should be "Hello" in Dealing With Forms example

Fixes #168
Add instructions on how to get XHP working in your codebase (i.e. installing XHP)

Fixes #128
Clowntown: I forgot to add the actual xhp install doc file to my git branch. Sigh. No wonder I was getting validation errors on the server.

Fixes #128
Make lambda example a bit more clear

Fixes #155