Find usages of step; Fixes #3

ftplugin/python/behave.vim

@@ -0,0 +1,24 @@
+"
+" Loads mapping for python files.
+"
+
+" Only do this when not done yet for this buffer
+if exists('b:did_ftplugin')
+    finish
+endif
+let b:did_ftplugin = 1
+
+" To use line continuation, remove 'C' from 'cpoptions'
+let s:cpo_save = &cpo
+set cpo&vim
+
+" :help undo_ftplugin
+" What should be stored depends on what will be changed in the ftplugin.
+let b:undo_ftplugin = 'setl com< cms< fo<'
+
+" Loads mapping for gherkin files.
+nnoremap <buffer> <localleader>b :call behave#find_usages()<cr>
+
+" Restore 'cpoptions'
+let &cpo = s:cpo_save
+unlet s:cpo_save