Add instructions about using nlohmann/json with the conda package manager

Closes #1400.

Closes #1405

- Catch 1.12.0 -> 1.12.2
- Google Benchmark 1.3.0 -> 1.4.1

Improve dump_integer performance

Fix x64 target platform for appveyor

Add some unit tests for formatting integers
to keep code coverage as before.

This benchmark is a sample of 1 million "small" integers
in range [-1000000 1000000) sampled from uniform distribution.

This commits implements a faster int2ascii inspired by "Fastware" talk given
by Andrei Alexandrescu.
See: https://www.youtube.com/watch?v=o4-CwDo2zpg

Updated year in README.md

Fixed broken links in the README file

Fixed broken links in the README file

Closes #1132.

docs: typo in README

inintended -> unintended

buildsystem: relax requirement on cmake version

Commit 73cc5089 (Using target_compile_features to specify C++ 11
standard) bumped the required cmake version, from 3.0 to 3.8, so
as to get the definition of target_compile_features().

However, target_compile_features() was introduced in cmake-3.1:
    https://cmake.org/cmake/help/v3.1/command/target_compile_features.html

And using cmake-3.1 is indeed sufficient to properly build.

As such, relax the minimum required version down to cmake-3.1,
so we can build on oldish, entreprise-grade distributions that
only have cmake-3.1 (or at least, don't have up to cmake-3.8).
Reported-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>

"V567 The modification of the 'position.chars_read_current_line' variable is unsequenced relative to another operation on the same variable. This may lead to undefined behavior."

 Added Support for Structured Bindings 

For further details, read https://github.com/nlohmann/json/issues/1388 and https://blog.tartanllama.xyz/structured-bindings/