Building native extensions.  This could take a while...
ERROR:  Error installing summarize:
	ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
creating Makefile

make "DESTDIR=" clean

make "DESTDIR="
compiling article.c
article.c:107:37: warning: passing 'const unsigned char *' to parameter of type 'const char *' converts between pointers to integer types with different sign [-Wpointer-sign]
  if ((aWord == NULL) || (0==strlen(aWord)) ||(NULL==aLine)) return;
                                    ^~~~~
/usr/include/string.h:82:28: note: passing argument to parameter here
size_t   strlen(const char *);
                            ^
article.c:109:68: warning: passing 'const unsigned char *' to parameter of type 'const gchar *' (aka 'const char *') converts between pointers to integer types with different sign [-Wpointer-sign]
  aLine->words = g_list_append (aLine->words, (gpointer) g_strdup (aWord));
                                                                   ^~~~~
/opt/local/include/glib-2.0/glib/gstrfuncs.h:216:52: note: passing argument to parameter 'str' here
gchar*                g_strdup         (const gchar *str) G_GNUC_MALLOC;
                                                     ^
2 warnings generated.
compiling dictionary.c
dictionary.c:28:10: fatal error: 'libxml/xmlmemory.h' file not found
#include <libxml/xmlmemory.h>
         ^
1 error generated.
make: *** [dictionary.o] Error 1

make failed, exit code 2

Gem files will remain installed in /Library/Ruby/Gems/2.0.0/gems/summarize-1.0.3 for inspection.
Results logged to /Library/Ruby/Gems/2.0.0/extensions/universal-darwin-13/2.0.0/summarize-1.0.3/gem_make.out