[Ko van der Sloot]

• added a fix for #100
  (where Frog created invalid FoLiA in a corner-case)
• improved api_test
• small code refactoring
• require libfolia >= 2.15, for correct working of word correction
• improved MWU code. Using Unicode strings and detecting MWU's with a starting
  Capital.

[Maarten van Gompel]

• .gitignore: added build dir