Create Popen::communicate overload for std::string (#82)

* Create Popen::communicate overload for std::string

* Create Popen::send overload for std::string

Author: Sokolmish

subprocess.hpp

@@ -1288,6 +1288,9 @@ class Popen
   int send(const char* msg, size_t length)
   { return stream_.send(msg, length); }
 
+  int send(const std::string& msg)
+  { return send(msg.c_str(), msg.size()); }
+
   int send(const std::vector<char>& msg)
   { return stream_.send(msg); }
 
@@ -1298,6 +1301,11 @@ class Popen
     return res;
   }
 
+  std::pair<OutBuffer, ErrBuffer> communicate(const std::string& msg)
+  {
+    return communicate(msg.c_str(), msg.size());
+  }
+
   std::pair<OutBuffer, ErrBuffer> communicate(const std::vector<char>& msg)
   {
     auto res = stream_.communicate(msg);