[feature] forward-slashes-in-wiki-names

**Purpose**
- Addresses [#1194](https://github.com/CenterForOpenScience/osf.io/issues/1194)
- Currently, a user can create a wiki page with forward slashes in the name, but those forward slashes will be replaced with spaces when the wiki page is created without giving any warning to the user. 

**Changes**
- This PR adds an alert if the user tries to create a wiki page with forward slashes in the page name.
![screen shot 2014-11-21 at 12 24 23 pm](https://cloud.githubusercontent.com/assets/7913604/5146332/5c2e2138-7179-11e4-9508-3994870006db.png)

**Side Effects**
- None expected