index_indicators check needs improvement.

[jpaulodit]

Issue description

When installing local package, the logical check on this line does not work correctly when package name has -i in it.

pipenv/pipenv/core.py

Line 1873 in 29eb73a

if any(s in line for s in index_indicators):

Actual result

Pipenv tries installing a package called -e

Steps to replicate

Suppose you have a local python package named like marathon-python-internal

pipenv install -e ../packages/marathon-python-lnternal/

This results in the code flow falling inside the IF condition vs some other package name that doesn't have the string -i in them eg

pipenv install -e ../packages/funniest/

pipenv, version 2018.7.1

[techalchemy]

hmmm yes, that is a problem.

[mlouielu]

Some points I want to know:

1. pipenv install -i https://foo.bar

In pipenv, it will include source in Pipfile and https://foo.bar

2. pipenv install -i https://foo -i https://bar

It will only include source in Pipfile and https://bar

3. pipenv install -i https://foo --extra-index-url https://bar

It should include source in Pipfile, and https://foo, and https://bar

Is that right @techalchemy ?