Fix hygiene of macros

mainargs/src/Macros.scala

@@ -146,7 +146,7 @@ class Macros(val c: Context) {
     _root_.mainargs.MainData.create[$returnType, $curCls](
       $methodName,
       $mainInstance,
-      Seq(..$argSigs),
+      _root_.scala.Seq(..$argSigs),
       ($baseArgSym: $curCls, $argListSymbol: _root_.scala.Seq[_root_.scala.Any]) => {
         $baseArgSym.${TermName(methodName)}(..$argNameCasts)
       }

mainargs/test/src/HygieneTests.scala

@@ -0,0 +1,26 @@
+package mainargs
+import utest._
+
+
+object HygieneTests extends TestSuite{
+
+  object Main{
+    @main
+    def run(@arg(short = 'f', doc = "String to print repeatedly")
+            foo: String,
+            @arg(name = "my-num", doc = "How many times to print string")
+            myNum: Int = 2,
+            @arg(doc = "Example flag")
+            bool: Flag) = {
+      foo * myNum + " " + bool.value
+    }
+  }
+
+  val tests = Tests {
+    import scala.collection.mutable._
+    test("importingSeqShouldntFailCompile"){
+      ParserForMethods(Main)
+    }
+
+  }
+}