Bind serve command to all local IPv4 interfaces

Easier when testing on multiple devices on the same network.
Added Google Closure Compiler JS optimizer as a filter
Add `minify_lines` filter

For use with HTML, CSS, JS, XML, SVG, you name it.

Strips leading whitespace on every line as well as empty and all-
whitespace lines. Minimalist minifier that is very useful with the
output Nikola produces.

Has no whitespace intelligence, so that must be exercised by user.
Will break in situations where whitespace is required or expected,
like Python in <pre> or CDATA. Can be worked around using escaped
whitespace (&#32; for space and &#9; for tab.) This filter could be
expanded to do that as its own pre-processing  if there is user-
demand. With this in place, it could be turned on by default.
document mathjax directive

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
flake8

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Document new filters
fix a tiny typo

[ci skip]
Let compilers override permalink’s extensions.

Fixes #1373
fix #1374 -- remove metadata comments in PHP files

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
fix tests

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
fix tests; fix #1340

Signed-off-by: Chris “Kwpolska” Warrick <kwpolska@gmail.com>
Handle PHP data through filters to avoid lxml/mako interference

Partially fixes #1375. Still need to force the filter for .php.
flake8 part 1

[ci skip]
flake8 part 2 + style changes

in two parts because I’m too lazy and using the one-file-at-once GitHub online editor.
Force php_template_injection filter on .php output

Issue #1375
Check for keys
Promote a different default filter
No need to duplicate this from post.tmpl
flake8
Revert "No need to duplicate this from post.tmpl"

Turns out it’s actually needed:

https://travis-ci.org/getnikola/nikola/jobs/31251801

cc @Aeyoun

This reverts commit 62a0699055ca5d26edcf598263fdc64d33bc17b0.