fix parsing of editable packages, fixes pypa#2714

Fix the parsing of an editable package. When the package name is '-e', it will
be concatenated with the next package in the list (which is the VCS URL).

pipenv/core.py

@@ -1764,7 +1764,9 @@ def do_install(
         line, index = split_argument(line, short="i", long_="index", num=1)
         line, extra_indexes = split_argument(line, long_="extra-index-url")
         package_names = line.split()
-        package_name = package_names[0]
+        package_name = package_names.pop(0)
+        if package_name == '-e':
+            package_name = " ".join([package_name, package_names.pop(0)])
         if len(package_names) > 1:
             more_packages = package_names[1:]
         else: