Update hash.h.md

doc/api/mruby/hash.h.md

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+### mrb_hash_new
+
+```C
+mrb_value mrb_hash_new(mrb_state *mrb);
+```
+
+Initializes a hash.
+#### Example
+
+In this example we read from a Ruby file inside C. The Ruby code will print what you pass as an argument
+and what class the passed in value is. This example initializes a hash. In pure Ruby doing this is equivalent
+to Hash.new.
+
+```C
+#include <stdio.h>
+#include <mruby.h>
+#include "mruby/hash.h" // Needs the hash header.
+#include "mruby/compile.h"
+
+
+int main(int argc, char *argv[])
+{   
+    mrb_state *mrb = mrb_open();
+    if (!mrb) { /* handle error */ }
+    mrb_value new_hash; // Declare variable.
+     FILE *fp = fopen("test_ext.rb","r");
+     new_hash = mrb_hash_new(mrb);  // Initialize hash.
+     mrb_value obj = mrb_load_file(mrb,fp);
+     mrb_funcall(mrb, obj, "method_name", 1, new_hash);
+     fclose(fp);
+     mrb_close(mrb);
+    return 0;
+}
+```
+
+#### test_ext.rb
+
+``` Ruby
+class Example_Class
+    def method_name(a)
+        puts a
+        puts a.class
+    end
+end
+Example_Class.new
+```
+
+### mrb_hash_set
+
+```C
+#include <stdio.h>
+#include <mruby.h>
+#include "mruby/hash.h" // Needs the hash header.
+#include "mruby/compile.h"
+
+
+int main(int argc, char *argv[])
+{   
+    mrb_state *mrb = mrb_open();
+    if (!mrb) { /* handle error */ }
+     mrb_value new_hash; // Declare variable.
+     mrb_sym hash_key = mrb_intern_cstr(mrb, "da_key"); // Declare a symbol.
+     mrb_int hash_value = 80; // Declare a fixnum value.
+     FILE *fp = fopen("test_ext.rb","r");
+     new_hash = mrb_hash_new(mrb);  // Initialize hash.
+     mrb_value obj = mrb_load_file(mrb,fp);
+     mrb_hash_set(mrb, new_hash, mrb_symbol_value(hash_key), mrb_fixnum_value(hash_value)); // Set values to hash.
+     mrb_funcall(mrb, obj, "method_name", 1, new_hash);
+     fclose(fp);
+     mrb_close(mrb);
+    return 0;
+}
+```
+
+#### test_ext.rb
+
+```Ruby
+class Example_Class
+    def method_name(a)
+        puts a
+        puts a.class
+    end
+end
+Example_Class.new
+```
+
+#### Result
+
+After compiling you should get these results.
+
+```Ruby
+{:da_key=>80}
+Hash
+```
+
+