Speedup and simplify tests

This drastically speeds up tests and simplifies test writing by making
it so that no explicit calls for waiting are needed. Elements that are
queried for now implicitly waits for them to be available.

On my machine, tests used to take 3-4 minutes to complete. Now they take
~1 minute to complete.

tests/browsertests/scenario1.nim

@@ -5,8 +5,6 @@ import webdriver
 proc test*(session: Session, baseUrl: string) =
   session.navigate(baseUrl)
 
-  waitForLoad(session)
-
   # Sanity checks
   test "shows sign up":
     session.checkText("#signup-btn", "Sign up")
@@ -38,10 +36,8 @@ proc test*(session: Session, baseUrl: string) =
       logout()
 
       navigate baseUrl
-      wait()
 
       register "TEst1", "test1", verify = false
 
       ensureExists "#signup-form .has-error"
-      navigate baseUrl
-      wait()
+      navigate baseUrl