Formatting issue in README

[Denis Sikuler]

There is a typo in README.md causing incorrect appearance of the following sentence:

To run GitterMobile on iOS you need to open ios/gittermobile.xcworkspace instead of ios/gittermobile.xcodeproj` in Xcode.

[Terry Sahaidak]

Hey @gamtiq. Did you mean missing `?

[Denis Sikuler]

Exactly.

[Terry Sahaidak]

@gamtiq, thank you :)