Avoid stopping function my_logs() at premium cache

[S0S-90]

see #117

I have changed the function my_logs() so that if cache can be read by guid it is read by guid and otherwise -- i. e. if the cache is only for premium members -- it reads the cache by the GC code. So my_logs() doesn't throw an error and you can get the information of the caches you have found before the PMonly cache. It is even possible to get some information on the PMonly cache by cache.load_quick().

[coveralls]

Coverage increased (+0.1%) to 94.517% when pulling 397b973 on S0S-90:master into b4cb385 on tomasbedrich:master.

[tomasbedrich]

Thank you for your PR. There are some minor problems, but in general it should work nice.

Please change the history (using git rebase -i) and remove unnecessary commit + its revert.

[S0S-90]

I've tried to implement your requested changes:

• changed history with 'git rebase -i HEAD~3'
• read gccode from redirected url (makes function _get_gccode_from_guidpage unnecessary)
• use self._request with stored URL to get the redirected url
• reformated doctring