Major refactor, don't expose constructor of Tiapp
move "is" functions to utils
move TiappError to own module
add some dummy modules
generic item group parser for XML
implement Tiapp.get() and add(), fixes #4 and fixes #5
docs and updates
platform only supports one value, fixes #7

details:
https://wiki.appcelerator.org/display/guides2/tiapp.xml+and+timodule.xml
+Reference#tiapp.xmlandtimodule.xmlReference-modules
add() options, fixes #6
validate add() by array, fixes #8
doc update
tested write(), fixes #3
doc updates
more API docs
add api link
fix api link
abstract out some xml calls
top level elements, fixes #12
more testing
semicolon