add verbose mode to pip

Fixes #727

pipenv/cli.py

@@ -1300,6 +1300,8 @@ def pip_install(
             if '--hash' not in install_reqs:
                 ignore_hashes = True
 
+        verbose_flag = '--verbose' if verbose else ''
+
         if not ignore_hashes:
             install_reqs += ' --require-hashes'
 
@@ -1309,13 +1311,14 @@ def pip_install(
         quoted_pip = which_pip(allow_global=allow_global)
         quoted_pip = shellquote(quoted_pip)
 
-        pip_command = '{0} install {4} {5} {3} {1} {2} --exists-action w'.format(
+        pip_command = '{0} install {4} {5} {6} {3} {1} {2} --exists-action w'.format(
             quoted_pip,
             install_reqs,
             ' '.join(prepare_pip_source_args([source])),
             no_deps,
             pre,
-            src
+            src,
+            verbose_flag
         )
 
         if verbose: