Adding support for execution on slurm grids

- Adding support for SlurmTaskExecutor in `daggyd` if DAGGY_ENABLE_SLURM is defined.
- Renaming some test cases
- Enabling compile-time slurm support
- Adding slurm documentation

tests/unit_threadpool.cpp

@@ -7,7 +7,7 @@
 
 using namespace daggy;
 
-TEST_CASE("Threadpool Construction", "[threadpool]") {
+TEST_CASE("threadpool", "[threadpool]") {
     std::atomic<uint32_t> cnt(0);
     ThreadPool tp(10);
 
@@ -22,7 +22,7 @@ TEST_CASE("Threadpool Construction", "[threadpool]") {
                 return cnt.load();
             })));
         tp.addTasks(tq);
-        for (auto &r : res) r.get();
+        for (auto &r: res) r.get();
         REQUIRE(cnt == 100);
     }
 
@@ -35,7 +35,7 @@ TEST_CASE("Threadpool Construction", "[threadpool]") {
                 cnt++;
                 return;
             }));
-        for (auto &r : res) r.get();
+        for (auto &r: res) r.get();
         REQUIRE(cnt == 100);
     }
 }