Restructured code, no functional changes.

Summary:
Moved implementation of classes declared in
ClangTidyDiagnosticConsumer.h to ClangTidyDiagnosticConsumer.cpp.
Added a FIXME note in ClangTidyDiagnosticConsumer::HandleDiagnostic.

Reviewers: klimek, djasper

Reviewed By: klimek

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D2520

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@198807 91177308-0d34-0410-b5e6-96231b3b80d8
Updated file comment.

git-svn-id: https://llvm.org/svn/llvm-project/clang-tools-extra/trunk@198808 91177308-0d34-0410-b5e6-96231b3b80d8