Sign in with GitHub Enterprise account does not work
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### Description

When I try to sign in with my companies GitHub Enterprise Account, I get two errors:
1. If I trie to sign in via "Sign in using your browser" a tab with a GitHub 404-page opens in the browser.
2. When I try to sign in via the Kactus-App itself, I get an error message telling me, that my GitHub Enterprise version is not up to date - which is not true, as we are using the latest available version (2.10.6).

### Version

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**Kactus version:** 0.2.6

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**OS version:** MacOS Sierra 10.12.6

### Steps to Reproduce

1. Click on "Publish Repository"
2. Click on Tab "Enterprise"
3. Click button "Sign In"
4. Enter enterprise server address
5. Enter username and password
6. Click button "Sign In"
7. Boom - Error Message 

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**Expected behavior:** Would expect to be able to login

**Actual behavior:** Error message (see above)

**Reproduces how often:** 5 times

### Logs

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2017-09-07T08:13:21.312Z - info: [ui] Stats reported.

#### Additional Information

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