Initial commit
range class code and helper functions and algorithms.

The range class provides an interface to combine to iterators representing
a range of objects and use them similarly to normal container classes.
add README
add small test programm
comment out copyright header. Oops
bugfixes
fix divide function
make has() a oneline function

Compilers don't seem to support relaxed constexpr of c++14 yet.
extend test programm
add minimal Makefile for test programm
add gitignore
Extend README
test: check range based for loops
back() was a multiline constexpr as well. Fix for now
test front() and back() functions
mark as much as possible as constexpr
range: add functions for growing and shrinking by one at either end
range: various fixes
range: add for_each to apply a function to two ranges