exceptions: Make Tlv::Error a base class for all packet-processing exceptions

This commit also includes a number of code style fixes.

Change-Id: I44f83915e733b43d5f43b4266902c8262e928d91
Refs: #1528
diff --git a/src/transport/transport.hpp b/src/transport/transport.hpp
index 08740fb..eda9521 100644
--- a/src/transport/transport.hpp
+++ b/src/transport/transport.hpp
@@ -12,7 +12,8 @@
 
 namespace ndn {
 
-class Transport {
+class Transport
+{
 public:
   class Error : public std::runtime_error
   {