Merge pull request #130 from tyborg/issue-129

Fixes amlcurran/ShowcaseView#129
Merge pull request #128 from tyborg/issue-127

Fixes amlcurran/ShowcaseView#127
Fixes amlcurran/ShowcaseView#135
Set a minimum width and height to prevent the negative width and the positions out of the screen.
Warning: This fix is not guarantees to not overflow the text at the bottom of the screen.
Merge remote-tracking branch 'remotes/ty/issue-135' into tymaster