GitRepository: hasChanges() calls `git update-index -q --refresh`

See czproject#17

GitRepository: createTag() - added parameter $options

It allows creating tags like `git tag -a -m "Tagging version v2.1.0" "v2.1.0"`

GitRepository: STDERR is redirected to STDOUT

GitRepository: added exit-code to exception message

GitRepository: isRemoteUrlReadable() - improved detection

See czproject#7 (comment)

GitRepository: isRemoteUrlReadable() - improved detection

See czproject#7 (comment)

GitRepository, IGit: added method addAllChanges()

GitRepository: cloneRepository() - added argument $params

Readme: updated

Readme: removed link to API documentation