Set TwitterAPI infos after build

[Thaodan]

It would make development easier if there was the abiltiy to set the twitter API key after build to allow automatic builds on buildservice or similar without storing the api key publicly.

[ljo]

It would also make switching keys easier. Especially useful now when API error message 'too many requests' shows up quite regularly.

[Wunderfitz]

Mhmm, I never get this "too many requests" error message. How many times per minute are you refreshing that you get this error?
Overall I'm open to any improvements to the build procedure, simply send in the PRs. ;)