Rename `dispatch` function to `fetchDispatch` to match the callsite in the async docs
Set<Tv>::contains(Tv k) checks for value existence, not key
Explicitly mention OutOfBoundsException
Point HHVM Installation to hacklang.org/install
Fix some typos and confusion with class_meth() and inst_meth()
Give search suggestion some space
Fix code that causes HHVM warnings and notices when viewing the docs. These fixes should remove all the doc based warnings we have been getting.

Test Plan:
All these errors go away. Error log file becomes more manageable.

HipHop Warning: File not found: /data/users/joelm/hack-hhvm-docs/includ
e/../manual/en/toc/langref.inc in /data/users/joelm/hack-hhvm-docs/incl
ude/layout.inc on line 652
HipHop Notice: Undefined variable: TOC in /data/users/joelm/hack-hhvm-d
ocs/include/layout.inc on line 657
HipHop Notice: Undefined variable: title in /data/users/joelm/hack-hhvm
-docs/include/layout.inc on line 667

Reviewers: jpearce, sgolemon

Reviewed By: jpearce

Differential Revision: https://phabricator.fb.com/D1244514
Some Map docs cleanup
Merge pull request #111 from ClaudiuC/fetchdispatch

Rename `dispatch` function to `fetchDispatch` to match the callsite
Merge pull request #112 from ClaudiuC/set_contains

Set<Tv>::contains() checks for value existence, not key
Merge pull request #113 from ClaudiuC/out_of_bounds

Explicitly mention OutOfBoundsException
Merge pull request #114 from ClaudiuC/hhvm_install

Point HHVM Installation to hacklang.org/install
Merge pull request #118 from ClaudiuC/maps

Some Map docs cleanup
Merge pull request #116 from ClaudiuC/search

Give search suggestion some space
Merge pull request #115 from ClaudiuC/meth_docs

Fix some typos and confusion with class_meth() and inst_meth()