Update minimum python version in README.md
Python 3.5 has been required since
@@ -13,7 +13,7 @@ build system.
#### Dependencies
- - [Python](http://python.org) (version 3.4 or newer)
+ - [Python](http://python.org) (version 3.5 or newer)
- [Ninja](https://ninja-build.org) (version 1.5 or newer)
#### Installing from source
