Update release notes and README. Ready release 0.9.0

Merge pull request guillermo-navas-palencia#63 from guillermo-navas-p…

…alencia/release_0.8.0

Release 0.8.0

Update release notes

Merge pull request guillermo-navas-palencia#45 from guillermo-navas-p…

…alencia/release_0.6.1

Update to version 0.6.1

Update setup.py to version 0.6.0

Merge pull request guillermo-navas-palencia#25 from guillermo-navas-p…

…alencia/release_0.5.0

Release 0.5.0

Update README.rst to version 0.4.0

Update to version 0.3.1

Merge pull request guillermo-navas-palencia#6 from guillermo-navas-pa…

…lencia/release_0.3.0

Release 0.3.0

Merge pull request guillermo-navas-palencia#4 from guillermo-navas-pa…

…lencia/release_0.2.0

Release 0.2.0