Version 1.4.0

Features:
 * Set debugger features with g:vdebug_features dictionary (issue #55)
 * Allow use of '~' in log files (issue #53)

Bug fixes:
 * Print error message if trying to start debugger with unsaved buffers (issue #57)
 * Don't allow visual eval outside of debugging session (issue #52)
 * Show updated key mappings in status window (issue #51)
 * Fix problem with stuck breakpoints after debugging (issue #48, #43)
 * Swap back to original tab after debugging session closes (issue #23)