fixed for ios 13 toolbar issue. and moved out some code to a new file. (

#9)

* fixed for ios 13 toolbar issue. and moved out some code to a new file.
* moved extensions under Sources folder
* fixed bottom constraint.

iPhone Xʀ with ios13 cant be found in travis ci, stick back with ipho…

…ne X. ios 11.3

Merge pull request #6 from michaelhenry/feature/able-to-hide-title

Feature/able to hide title