tab to space, improve comments typos (#302)

include/LightGBM/config.h

@@ -134,7 +134,7 @@ public:
   double sigmoid = 1.0f;
   double huber_delta = 1.0f;
   double fair_c = 1.0f;
-  // for ApproximateHessianWithGaussian
+  // for Approximate Hessian With Gaussian
   double gaussian_eta = 1.0f;
   double poisson_max_delta_step = 0.7f;
   // for lambdarank

src/application/application.cpp

@@ -33,7 +33,7 @@ Application::Application(int argc, char** argv) {
     omp_set_num_threads(config_.num_threads);
   }
   if (config_.io_config.data_filename.size() == 0) {
-	  Log::Fatal("No training/prediction data, application quit");
+    Log::Fatal("No training/prediction data, application quit");
   }
 }
 

src/io/config.cpp

@@ -104,7 +104,7 @@ void OverallConfig::GetMetricType(const std::unordered_map<std::string, std::str
     std::transform(value.begin(), value.end(), value.begin(), Common::tolower);
     // split
     std::vector<std::string> metrics = Common::Split(value.c_str(), ',');
-    // remove dumplicate
+    // remove duplicate
     std::unordered_set<std::string> metric_sets;
     for (auto& metric : metrics) {
       std::transform(metric.begin(), metric.end(), metric.begin(), Common::tolower);