Disable Git.clone() test

This test fails on Travis as cloning from GitHub requires accepting the
host authenticity, expects user input and eventually fails on timeout.
It makes sense to uncomment this test only locally.

test/index.test.coffee

@@ -40,6 +40,7 @@ describe "git", ->
     after (done) ->
       exec "rm -rf #{newRepositoryDir}", done
 
+  ###
   describe "clone()", ->
     @timeout 30000
     repo = null
@@ -55,3 +56,4 @@ describe "git", ->
         done()
     after (done) ->
       exec "rm -rf #{newRepositoryDir}", done
+  ###