Fix core dump in chromobius by adding try-catch to main.cc (#39)

Currently, if one runs `chromobius` without any arguments, it prints the
help text but also produces a core dump. This happens because the end of
`src/chromobius/commands/main_all.cc` has

```cpp
throw std::invalid_argument(ss.str());
```

and this is not caught by `src/main.cc`. This commit adds a
`try`-`catch` to `src/main.cc` to catch the exception and exit with a
failure code. (This behavior is similar to what `main.perf.cc` does to
exit with an error.)

Author: mhucka

src/main.cc

@@ -12,8 +12,16 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+#include <iostream>
+#include <stdexcept>
+
 #include "chromobius/commands/main_all.h"
 
-int main(int argc, const char **argv) {
-    return chromobius::main(argc, argv);
+int main(int argc, const char** argv) {
+    try {
+        return chromobius::main(argc, argv);
+    } catch (const std::invalid_argument& ex) {
+        std::cerr << ex.what() << std::endl;
+        exit(EXIT_FAILURE);
+    }
 }