consistency

~ reworded memory allocation errors to be more consistent with other
  error messages
+ added usage guide if wrong usage is used

src/datastream.c

@@ -24,7 +24,7 @@ char* piped_data() {
 			bufferSize += 256;
 			char *newBuffer = realloc(inputBuffer, bufferSize);
 			if (!newBuffer) {
-				fprintf(stderr, "Memory allocation error\n");
+				fprintf(stderr, "Error: Memory allocation\n");
 				free(inputBuffer);
 				exit(1);
 			}
@@ -37,7 +37,7 @@ char* piped_data() {
 		bufferSize += 1;
 		char *newBuffer = realloc(inputBuffer, bufferSize);
 		if (!newBuffer) {
-			fprintf(stderr, "Memory allocation error\n");
+			fprintf(stderr, "Error: Memory allocation\n");
 			free(inputBuffer);
 			exit(1);
 		}

src/main.c

@@ -50,6 +50,7 @@ int main(int argc, char** argv) {
 	// invalid command was used
 	if (lActionIndex == ActionsCount) {
 		fprintf(stderr, "Error: Invalid Argument: %s\n", cmd);
+		print_usage();
 		return 1;
 	}