Client-side validation in tags filter

When invalid tag entered in tags filter, user should be notified by pop-up or smth like that.

Acceptance criteria:

1. Comma (",") should separate two different tags. After user entered tag and pressed comma, tag appeared in field and user can enter next tag.
2. If user searching by empty query - main page should appear.
3. User should be able search by tags which contains number.
4. User should be able search by tag which contains space, as example: python 3
5. User should be able search by tag which contains special symbols, as example: python 3.3, C++
6. Query which only contains special characters return no results. (Tag with special characters can not be created)
7. Spaces before and after tag should be truncated
8. If user entered the same tags - all except one should be truncated.