Ignore hphp/hack/Makefile
Stop setting global variables, it can conflict with other plugins

Specifically is *does* conflict with YouCompleteMe that imports it's own `base` module. Python support in vim is buggy, but this is an easy fix.
Closes #2117
Github Author: James Miller <jamespocketrent.com>

Reviewed By: @toroman

Differential Revision: D1232398
Update HHI files

Adds the differenceByKey() signature, corrects the toImmMap() return type.

Adds the SleepWaitHandle and SessionScopedWaitHandle classes.
Closes #2112
Github Author: Simon Welsh <simonsimon.geek.nz>

Reviewed By: @elgenie

Differential Revision: D1232083
support for Stringish

Typechecker counterpart to {D1214064}: Stringish is
 implemented implicitly by any object with a __toString, and also has
 "string"s as a subtype

Reviewed By: @jwatzman

Differential Revision: D1215427
Allow the "hh" file extension

Open source code is starting to use this, let's actually
support it :)

Reviewed By: @pikatchu

Differential Revision: D1239257