Merge pull request #156 from Geod24/variant

Remove useless imports to std.variant
merged-on-behalf-of: Sebastian Wilzbach <sebi.wilzbach@gmail.com>

source/vibe/core/concurrency.d

@@ -16,7 +16,6 @@ import core.time;
 import std.traits;
 import std.typecons;
 import std.typetuple;
-import std.variant;
 import std.string;
 import vibe.core.task;
 

source/vibe/core/core.d

@@ -29,7 +29,6 @@ import std.range : empty, front, popFront;
 import std.string;
 import std.traits : isFunctionPointer;
 import std.typecons : Flag, Yes, Typedef, Tuple, tuple;
-import std.variant;
 import core.atomic;
 import core.sync.condition;
 import core.sync.mutex;

source/vibe/core/task.d

@@ -15,7 +15,6 @@ import core.thread;
 import std.exception;
 import std.traits;
 import std.typecons;
-import std.variant;
 
 
 /** Represents a single task as started using vibe.core.runTask.