Fix README

Use full path for gif in README so it shows up correctly in CocoaPods docs.

Horizontal padding, left & right views, bug fixes

New features:

• #14 Added horizontal padding. Thanks @bobbyrehm!
• #18 Added support for left and right views. Thanks @RaoulNL!

Updates:

• Updates to Xcode settings and storyboard for Xcode 9.3
• Bumped min deployment target to iOS 10.0
• Modernised constraints in MFTextField

Bug fixes:

• #17 Fix crash when attributed placeholder is nil
• #20 Fix both floating & inline placeholders being shown when text is cleared

iOS 11 bug fixes

• #12 Fix truncated text on iOS 11
• #11 Fix crash when attributed string is empty

Bug fixes & README updates

• Fix issue #4: Error label isn't properly laid out if it already exists when the view is loaded
• Fix infinite loop & crashes caused by calls to [self layoutIfNeeded]
• Update README with Carthage installation instructions and demo gif

Initial release

Simple Material Design text field with animated placeholder label and error message.