Add missing header includes

For some reason, xcode tolerated these missing includes.
Travis CI doesn't.

include/tree_sitter/compiler.h

@@ -5,6 +5,7 @@
 #include <map>
 #include <set>
 #include <string>
+#include <memory>
 
 namespace tree_sitter {
     namespace rules {

src/compiler/build_tables/item_set_closure.cpp

@@ -2,6 +2,7 @@
 #include "tree_sitter/compiler.h"
 #include "./follow_sets.h"
 #include "item.h"
+#include <algorithm>
 
 namespace tree_sitter {
     using std::set;

src/compiler/rules/rule.h

@@ -2,6 +2,7 @@
 #define __TreeSitter__rule__
 
 #include <string>
+#include <memory>
 
 namespace tree_sitter {
     namespace rules {

src/compiler/rules/symbol.h

@@ -2,7 +2,7 @@
 #define __tree_sitter__sym__
 
 #include "rule.h"
-#include <map>
+#include <utility>
 
 namespace tree_sitter  {
     namespace rules {

src/runtime/error.cpp

@@ -1,5 +1,6 @@
 #include "tree_sitter/runtime.h"
 #include <string>
+#include "string.h"
 
 using std::string;