clang-format: [JS] Sort imports case insensitive.

Summary: ASCII case sorting does not help finding imported symbols quickly, and it is common to have e.g. class Foo and function fooFactory exported/imported from the same file.

Reviewers: djasper

Subscribers: klimek, cfe-commits

Differential Revision: http://reviews.llvm.org/D22146

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@274977 91177308-0d34-0410-b5e6-96231b3b80d8