xAxis first label offset and overlaps on second label

## What did you do?

Rendered a bar chart using charts on iOS

## What did you expect to happen?

Render normally without any label overlaps

## What happened instead?

First label on xAxis is off and overlaps the next label

## Charts Environment

**Charts version/Branch/Commit Number:** 3.1.1
**Xcode version:** 9.4.1
**Swift version:** 4.1.2
**Platform(s) running Charts:** iPhone 7, iPhone 8, iPhone X
**macOS version running Xcode:** 10.13.5

## Screenshot