Use try_files in Nginx config to serve docs.

Should handle /en/latest/ URLs, as well as single_version URLs.
Add language selection to nav at lower left
Create /translations/en directory before symlinking.

One of the last steps of the build process is to create the symlink
for /translations/en/, but the directory must exist before attempting
to symlink.
Create single_version symlink.
Merge pull request #599 from rtfd/issue-598-fix-translation-symlink

Create /translations/en directory before symlinking.
Merge pull request #597 from maskit/feature/language-selection

Add language selection to nav at lower left
Preserve scheme (http or https) in rewrite rule.
Only show languages if we have translations
Add nginx-smoke-test.py.

Run this test script to verify that a change to
the Nginx configuration behaves correctly.
Fix logic from 6f5e8f5
Merge pull request #603 from toffer/bugfix-602-https-redirect-to-http

Preserve scheme (http or https) in rewrite rule.
Include pandoc. Refs #579
Specify pip version
Fix canonical page logic for single page sites
Single version*
Merge pull request #600 from rtfd/issue-293-part-two

Issue 293 part two
Fix canonical page variable placement
Use unicode string for format. Fixes #568.
Fix tasks logger too
Use https github links. Fixes #539.