updated version string

0.7.0rc12

0.7.0rc12
  - fixed issue pyscada#13, Mismatch between event limit elif cases and the
displayed limit types.
  - merged pull request pyscada#12, changing from source_format to
target_format to match preceding setting of '2H' value

0.7.0rc11

0.7.0rc11
  - changed widget model to support content from plugins
  - changed visable to visible in pyscada.hmi.models.Chart,
SlidingPanelMenu, Widget
  - some changes for python 3 compatibility in pyscada.export

0.7.0rc10

0.7.0rc10
  - updated docs
  - fixed no data download in pyscada.js
  - fixed default pollingt interval in pyscada.device

updated to 0.7.0rc4

0.7.0rc4
- added missing migration file

moved tag

updated readme