create reusable input field.

[FarahZaqout]

Input field component:

The component should be usable across the website. For that, it needs to take different types, different classes, and different placeholders, values and names.

Acceptance criteria:

• sufficiently tested.
• props are validated.
• props include type, class, placeholder, value, and name.
• component should be stateless function.

relates #32

[FarahZaqout]

day1: finalized all the required input props with validation

Stopped working yesterday and today to fix urgent issues with Travis, along with @amusameh and @ashatat.

What remains is to make sure it's well tested. Will resume working on it later today (jest tests).

[FarahZaqout]

Component should be ready for review by the end of tomorrow at most.

[FarahZaqout]

Must read jest and use it on another independent repo.