[clang-tidy] Refactor: Move readability checks to namespace clang::tidy::readability

clang-tidy checks are organized into modules. This refactoring moves the
readability module checks into the namespace clang::tidy::readability

http://reviews.llvm.org/D7997

Patch by Richard Thomson!

llvm-svn: 230946
diff --git a/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp b/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp
index be7e31e..e6e652c 100644
--- a/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp
+++ b/clang-tools-extra/clang-tidy/readability/ShrinkToFitCheck.cpp
@@ -39,6 +39,7 @@
 
 namespace clang {
 namespace tidy {
+namespace readability {
 
 void ShrinkToFitCheck::registerMatchers(MatchFinder *Finder) {
   // Swap as a function need not to be considered, because rvalue can not
@@ -104,5 +105,6 @@
       << Hint;
 }
 
+} // namespace readability
 } // namespace tidy
 } // namespace clang