Release 0.3.1

 BUG FIXES

 * Ensure submodules are refreshed for merge conflict detection
   (rschlaikjer, #73, #75)
 * Ensure the proper remote is fetched for merge conflict detection
   (rschlaikjer, #74, #75)
 * Hard reset and clean pre-checkout to prevent checkout being blocked
   by unstaged changes (rschlaikjer, #76)
 * Force delete / recreate of test branches, to fix branches that
   might not have been cleaned up properly (rschlaikjer, #76)

 PERFORMANCE TWEAKS

 * For performance reasons, only perform a fetch when a new remote or
   pickme has been added (rschlaikjer, #76)