FIX: allow underscore and dash in username search

_ and - are technically punctuations, but we allow them in usernames so
accept them in search

test/javascripts/lib/user-search-test.js.es6

@@ -89,6 +89,8 @@ QUnit.test("it skips a search depending on punctuations", async assert => {
   let allowedTerms = [
     "@sam sam", // double space is not allowed
     "@sam.sam",
+    "@sam_sam",
+    "@sam-sam",
     "@"
   ];