correctly type Cosets methods

tc/test/test_solve.cpp

@@ -8,7 +8,12 @@
 int main(int argc, char *argv[]) {
     std::string key = argv[1];
 
-    std::vector<std::tuple<std::string, tc::Group, std::vector<tc::Coset>, size_t>> groups;
+    std::vector<std::tuple<
+        std::string,
+        tc::Group,
+        std::vector<tc::Gen>,
+        size_t
+    >> groups;
 
     // See the group orders here https://en.wikipedia.org/wiki/Coxeter_group#Properties
     if (key == "A") {