buffet: Remove 'chromeos' namespace and move everything to buffet NS

As discussed, moved all the classes out of chromeos namespace into
'buffet.

Also fixed a number of cpplint's warnings.

BUG=None
TEST=Everything still compiles and unit tests succeed.

Change-Id: Ide864acb2504627404966727f66d353af60e531d
Reviewed-on: https://chromium-review.googlesource.com/198971
Reviewed-by: Christopher Wiley <wiley@chromium.org>
Commit-Queue: Alex Vakulenko <avakulenko@chromium.org>
Tested-by: Alex Vakulenko <avakulenko@chromium.org>
diff --git a/buffet/error_unittest.cc b/buffet/error_unittest.cc
index 3963315..cf943ad 100644
--- a/buffet/error_unittest.cc
+++ b/buffet/error_unittest.cc
@@ -7,15 +7,15 @@
 
 #include "buffet/error.h"
 
-using chromeos::Error;
+using buffet::Error;
 
 namespace {
 
-chromeos::ErrorPtr GenerateNetworkError() {
+buffet::ErrorPtr GenerateNetworkError() {
   return Error::Create("network", "not_found", "Resource not found");
 }
 
-chromeos::ErrorPtr GenerateHttpError() {
+buffet::ErrorPtr GenerateHttpError() {
   auto inner = GenerateNetworkError();
   return Error::Create("HTTP", "404", "Not found", std::move(inner));
 }