adding support for custom interpolation tags

moved interpolation regex and char to lib/adapter.js

added public methods to index.js which allow updating the interpolation adapter

added test for custom interpolation tag adapter

updated Readme.md with interpolation adapter

updated custom interpolation api (hasInterpolation not safe!)

applied not working workaround for hasInterpolation

fixed hasInterpolation with one single regex

added support for flags in interpolation regex
updated interpolate alogirthm

Changed `interpolation.regex` to be compatiable with new interpolation
algorithm

Fixed custom interpolation methods and tests
Added support for variable-length interpolation delimters
Merge branch 'custom-interpolation' of github.com:bodokaiser/reactive into custom-interpolation