Compiling with clang and gcc with -Wshadow

See issue #17

Somewhere along the way we've also broken our ability to compile with GCC 4.7.3.  We'll have to decide if we care about
supporting 4.7.3 or not.  The changes that break this are:

-there is no emplace in std::map (or related) in 4.7.3
-there are some enable_ifs in rapidjson's writer.h that are always false (which is fine), but
GCC 4.7.3 doesn't like this

performance.cpp

@@ -344,13 +344,13 @@ int main()
   const bool randomize = false;
 
   //########################################
-  auto vectorDoubleTest = [&](size_t s, bool randomize)
+  auto vectorDoubleTest = [&](size_t s, bool randomize_)
   {
     std::ostringstream name;
     name << "Vector(double) size " << s;
 
     std::vector<double> data(s);
-    if(randomize)
+    if(randomize_)
       for( auto & d : data )
         d = rngD();
 
@@ -363,13 +363,13 @@ int main()
   vectorDoubleTest(1024*1024, randomize); // 8MB
 
   //########################################
-  auto vectorCharTest = [&](size_t s, bool randomize)
+  auto vectorCharTest = [&](size_t s, bool randomize_)
   {
     std::ostringstream name;
     name << "Vector(uint8_t) size " << s;
 
     std::vector<uint8_t> data(s);
-    if(randomize)
+    if(randomize_)
       for( auto & d : data )
         d = rngC();