Treat 'zh' as if it were 'zh-Hans' (that is, use Simplified Chinese).

Change-Id: Ic2e938b6dcc941f6356457d76f496ef8403873df
Match language codes case-insensitively.

There is a canonical case for language codes, but authors often use
all lowercase.

Change-Id: Id0f929b980602148d28a364889ed402d0795084a
Save and restore stack of inline decorations around environments, \item, etc.

Change-Id: I4f29b1df5b0db01dbbdbc3139f9c97ad53b4f3ee
Fix node 0.8 builds on travis by updating npm only to 1.4.28.

Node v0.8 is incompatible with npm 2.0.2, and it can't upgrade directly
to npm 2.0.x in one step in any case.

Change-Id: I3b75e917016a1f3ff6b3dc94fcce69943d5069c8