Return a Temporary from *Binding::Wrap.

Returning a JS<T> is GC-unsafe.

This commit also includes some cleanup around Node and Document reflection.
Enable rust-phf build and bump rust-phf submodule ptr.
Merge pull request #2804 from glennw/enable-phf

Enable rust-phf build and bump rust-phf submodule ptr.
Correct the allowed MPL licenses in licenseck.
Remove a glob import from tidy.py.
Remove unused code from tidy.py.
Stop using fileinput in tidy.py.

The code is expressed much more clearly with a loop over the files instead.
Fix PEP8 violations in tidy.py.
Test for trailing spaces in tidy.py.
Test for missing newlines at end of file in tidy.py.
Test for tabs in tidy.py.
Test for carriage returns in tidy.py.
Run tidy.py on Travis.
Merge pull request #2806 from Ms2ger/tidy

Improve and extend tidy.py, and run it on Travis.
Remove some dead code and fix some pyflakes warnings in CodegenRust.py.
adding 2 new default arguments when running make check-wpt so that it does not fail saying KeyError: 'debug_args' or KeyError: 'interactive'
Update run.py

None and False are better values here (thanks to @jgraham).
Merge pull request #2801 from Ms2ger/wrap-temp

Return a Temporary from *Binding::Wrap.
Merge pull request #2807 from Ms2ger/pyflakes-2

Remove some dead code and fix some pyflakes warnings in CodegenRust.py.
Store proxy handlers in a static array rather than a hashtable per window.