Please make throw optional (ie support build without exceptions) #196

What steps will reproduce the problem?
1. Include standard yaml-cpp headers from a c++ file and build with gcc using 
-fno-exeptions

What is the expected output? What do you see instead?
The build breaks with the following error:

In file included from /usr/include/yaml-cpp/node.h:132:0,
                 from /usr/include/yaml-cpp/yaml.h:13,
                 from /home/dev00/dev/cpp/PuzzleGame/DuckLib/DuckUtils/ObjectLoader.cpp:10:
/usr/include/yaml-cpp/nodeimpl.h: In instantiation of ‘const YAML::Node* 
YAML::Node::FindValue(const T&) const [with T = std::basic_string<char>]’:
/usr/include/yaml-cpp/nodeimpl.h:69:36:   required from here
/usr/include/yaml-cpp/nodeimpl.h:33:26: error: exception handling disabled, use 
-fexceptions to enable

I would really appreciate an #ifdef or equivalent to make sure "throw" 
statements can be left out. I know this can leave some errors undetected but 
it's a requirement to have exceptions disabled in my project. Having some error 
state to check or some return value wherever possible would be ideal.

What version of the product are you using? On what operating system?
yaml-cpp 0.3.0 from portage on Sabayon Linux 64-bit

Please provide any additional information below.
grepping for "throw" in the "include" directory yields:
./node/detail/impl.h:64:                    throw BadSubscript();
./node/detail/impl.h:92:                    throw BadSubscript();
./node/detail/impl.h:135:                    throw BadInsert();
./node/impl.h:106:                throw TypedBadConversion<T>();
./node/impl.h:111:            throw TypedBadConversion<T>();
./node/impl.h:122:                throw TypedBadConversion<std::string>();