Implemented and tested Toy_String, read more

Strings are needed for the handling of identifiers in the key/value
variable storage, so I've got them working first. I used the rope
pattern, which seems to be quite an interesting approach.

I'll add comparison checks later.

Adjusted how buckets are handled in all tests, could've been an issue
down the line.

Added the build instructions to README.md.

source/toy_string.h

@@ -0,0 +1,43 @@
+#include "toy_common.h"
+
+#include "toy_memory.h"
+
+//rope pattern
+typedef struct Toy_String {             //32 | 64 BITNESS
+	enum Toy_StringType {
+		TOY_STRING_NODE,
+		TOY_STRING_LEAF,
+	} type;                             //4  | 4
+
+	int length;                         //4  | 4
+	int refCount;                       //4  | 4
+
+	union {
+		struct {
+			struct Toy_String* left;    //4  | 8
+			struct Toy_String* right;   //4  | 8
+		} node;                         //8  | 16
+
+		struct {
+			int dummy;                  //4  | 4
+			char data[];                //-  | -
+		} leaf;                         //4  | 4
+	} as;                               //8  | 16
+} Toy_String;                           //20 | 28
+
+TOY_API Toy_String* Toy_createString(Toy_Bucket** bucket, const char* cstring);
+TOY_API Toy_String* Toy_createStringLength(Toy_Bucket** bucket, const char* cstring, int length);
+
+TOY_API Toy_String* Toy_copyString(Toy_Bucket** bucket, Toy_String* str);
+TOY_API Toy_String* Toy_deepCopyString(Toy_Bucket** bucket, Toy_String* str);
+
+TOY_API Toy_String* Toy_concatString(Toy_Bucket** bucket, Toy_String* left, Toy_String* right);
+
+TOY_API void Toy_freeString(Toy_String* str);
+
+TOY_API int Toy_getStringLength(Toy_String* str);
+TOY_API int Toy_getStringRefCount(Toy_String* str);
+
+TOY_API char* Toy_getStringRawBuffer(Toy_String* str); //allocates the buffer on the heap, needs to be freed
+
+//TODO: compare