Fixes #2378

Add note to Element.empty that GC is not used.
Fixes #2515

Doc changes to Request.md to correctly reflect argument `async` in the options of Request.
Fixing Browser.ie for new IE11 UA string.
Browser: Use 'rv:' field of UA for modern IE version.

References:

- #2534
- #2539
Browser: For modern IE (that is IE > 10), set Browser.modernie, for others we keep Browser.ie.

Rationale:

The primary use of `Browser.ie` is activating legacy code, such legacy
code is no longer required in modern IE (and may not even work anymore).
Keeping `Browser.ie == true` for modern IE would do more harm than good,
even though it's technically correct. Since everyone seems to agree UA
sniffing should be phased out, this technical incorrectness shouldn't
cause any problems. Moreover, `Browser.ie11` will still work and
`Browser.name` will still equal "ie".

References:

- #2534
- #2539
merge: IE11 UA string detection (Browser.modernie). (#2534, #2539)

Based on work by @dez87 in #2539.
Created task to build MooTools

`grunt build:all` is working.
`grunt build:nocompat` is having trouble removing the `.*compat` blocks.
Fixed nocompat build.
Using grunt-mootools-packager
merged 1.x specs into a single directory. removed unnecessary files.
Forgot to merge Native -> Types
Fixing YAML headers.
updated 'specs' task to build the specs set for the module or file. noticed some specs are using jasmine pre 1.0. Updating next.
fixed specs to  jasmine 1.x
Missed a couple of migrations.
Added sinon
Add blocks related with 1.2 specs no longer applicable in nocompat
Fixing Array and String dependencies. Updated Specs for compat.
 - Some are still broken
moved browser related specs to browser from string.
Removing merge problems