Version 1.56

FEATURE: a log file (containing errors and warnings) is now written to the corpus directory at the end of the corpus creation process;

FEATURE: downloaded files are now assigned an extension based on the mimetype reported by the remote server (previously they were assigned the same extension as the URL they were downloaded from);

BUGFIX: Fixed a bug that made the Windows version of BootCaT crash while downloading files with colons in the filename extension;