Nimble considers URL deps different from name deps

and it installs the same package again, at a version tag, even though
@#head was already available, then it errors out: 68bb97f30a/src/nimble.nim (L198)
- added a .gitignore for the "tests" dir

.gitignore

@@ -0,0 +1 @@
+/tests

bncurve.nimble

@@ -7,8 +7,8 @@ skipDirs      = @["tests", "Nim", "nim"]
 
 ### Dependencies
 
-requires "nim > 0.18.0"
-requires "https://github.com/cheatfate/nimcrypto"
+requires "nim > 0.18.0",
+         "nimcrypto"
 
 task test, "Run all tests":
   exec "nim c -f -r -d:release tests/tarith"