SwiftLint integration

[Garfeild]

This PR introduces SwiftLint to the project and fixes majority of lint warnings. SwiftLint is integrated as Xcode Plugin to ensure every contributor is using it.

Resolves #86

[okwasniewski]

Overall looks good! Thanks for this improvement, left few questions

[okwasniewski]

When it comes to auto formatting the code in Xcode for example on save. Is it possible with SwiftLint only or do we need something like SwiftFormat for that? We can add auto formatting in a separate PR but Im not that familliar with Swift tooling

[Garfeild]

When it comes to auto formatting the code in Xcode for example on save. Is it possible with SwiftLint only or do we need something like SwiftFormat for that? We can add auto formatting in a separate PR but Im not that familliar with Swift tooling

It's possible for sure. There are two ways of doing it, both will require to use binary and some small shell script in Xcode project itself.

• Use binary available on developer machine and throw error if it's missing. Biggest downside, folks will have to install exact version, which could be tricky for Homebrew users (there is no notion of pinned versions). Different versions also might have different set of rules (in many cases new rules are added).
• Add binary to the repository so we always have the right version. Problem? Well, we will have binary file in the repository, which is not a big of an issue overall.

[okwasniewski]

Thanks for explaining and huge amount of work! Let's for now use only SwiftLint as it's a big improvement itself.

I've created separate issues to enable each commented out rule:

• Enable force_unwrapping SwiftLint rule #93
• Enable implicitly_unwrapped_optional SwiftLint rule #94
• Enable no_magic_numbers SwiftLint rule #95