Travis-CI: Add assume-yes to install section

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Travis-CI: install dependencies in install section

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add extra version variable and get method

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add SpecFile.set_extra_version() draft

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add basic test for set_extra_version()

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add methods for getting full release string and release number

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add method for setting release number

Signed-off-by: Tomas Hozza <thozza@redhat.com>
Add methods for redefining Release with macro, and revert method

Signed-off-by: Tomas Hozza <thozza@redhat.com>