Changed done_column_name_regex to done_columns

[namangupta01]

Fixes #189 Currently user have to write regex expression in .trollolorc file and even after writing regex expression done_column_name_regex was coming as an array of string but we need regex expression there so here array is converted into regex expression on the spot this also allows to write done_columns easily in the .trollolorc file

[Ana06]

@namangupta01 it needs to be a regular expression because normally you have several Done columns with the number of the Sprint: Done 1, Done 2, Done 3,... or Done Sprint 1, Done Sprint 2, Done Sprint 2,...