Added support for XDG_COFIG_HOME

[mayanksuman]

If XDG_COFIG_HOME is set on the machine then make the config inside it.
Otherwise the config file is made in ~/.config/.
Default config file name has changed to tldr.py.conf

[codecov-io]

Codecov Report

Merging #41 into master will not change coverage.
The diff coverage is n/a.

@@          Coverage Diff          @@
##           master    #41   +/-   ##
=====================================
  Coverage     100%   100%           
=====================================
  Files           4      4           
  Lines         158    158           
=====================================
  Hits          158    158

Impacted Files	Coverage Δ
tldr/cli.py	100% <ø> (ø)	⬆️
tldr/config.py	100% <ø> (ø)	⬆️

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[lord63]

Closed, this is a break change, you can specify TLDR_CONFIG_DIR environment variable to set config dir.