Review corrections

Corrected stylistic mistakes and simplified a couple of the new tests.

include/turtle/matcher.hpp

@@ -41,7 +41,7 @@ public:
     explicit matcher(const char* expected) : expected_(expected) {}
     bool operator()(const char* actual)
     {
-        if (nullptr == actual || nullptr == expected_)
+        if(!actual || !expected_)
             return actual == expected_;
         return std::strcmp(actual, expected_) == 0;
     }

include/turtle/stream.hpp

@@ -108,7 +108,7 @@ namespace detail {
     }
     inline void serialize(stream& s, const char* const str)
     {
-        if (nullptr != str)
+        if(str)
             s << '"' << str << '"';
         else
             s << "nullptr";