Port to Windows

[osteele]

See https://ci.appveyor.com/project/osteele/liquid:

# github.com/osteele/liquid/strftime
could not determine kind of name for C.localtime_r
Command exited with code 2

[osteele]

This package no longer depends uses the C stdlib implementation of strftime. The remaining issue is time zones:

--- FAIL: TestStrftime (0.02s)
	Error Trace:	strftime_test.go:63
	Error:      	Not equal: 
	            	expected: "EST"
	            	actual: ""
	Messages:   	Strftime "%Z"
--- FAIL: TestStrftime_zones (0.00s)
	Error Trace:	strftime_test.go:146
	Error:      	Not equal: 
	            	expected: "%z=-0500 %Z=EST"
	            	actual: "%z=+0000 %Z=EST"
	Messages:   	02 Jan 06 15:04 EST
FAIL
FAIL	github.com/osteele/liquid/strftime	0.151s

– https://ci.appveyor.com/project/osteele/liquid

[osteele]

The problematic code (and test) now live in https://github.com/osteele/tuesday.

osteele/tuesday#1 is the upstream issue.