loosen version constraints
single entry point for concrete apis
Merged in digitalkaoz/bitbucket-api/single_entry_point (pull request #21)

single entry point for concrete apis
Merged in digitalkaoz/bitbucket-api/composer_fixes (pull request #20)

loosen version constraints
updated composer.lock
bumped version to 0.6.0
updated CHANGELOG
Merge branch 'release/0.6.0'
Merge tag '0.6.0' into develop

0.6.0