fix for #29 which does not trigger flake8 for removed files

that is accomplished by using --diff-filter parameter in git diff (taken from http://stackoverflow.com/questions/6879501/filter-git-diff-by-type-of-change)

also this commit changes the log level from error to info when particular VCS is not found

flake8diff/flake8.py

@@ -129,7 +129,7 @@ def get_vcs(self):
             try:
                 vcs = vcs(self.commits, self.options)
             except VCSNotInstalledError:
-                logger.error('Seems like {0} is not installed'.format(vcs.name))
+                logger.info('Seems like {0} is not installed'.format(vcs.name))
             else:
                 if vcs.is_used() and vcs.check():
                     return vcs

flake8diff/vcs/git.py

@@ -20,7 +20,7 @@ def get_vcs(self):
         """
         Get git binary executable path
         """
-        return _execute('which git', strict=True).strip()
+        return _execute('which git', strict=True, log_errors=False).strip()
 
     def is_used(self):
         """
@@ -64,6 +64,7 @@ def changed_files(self):
             self.vcs,
             "diff",
             "--name-only",
+            "--diff-filter=ACMRTUXB"
         ] + self.commits)
 
         return filter(self.filter_file,

flake8diff/vcs/hg.py

@@ -20,7 +20,7 @@ def get_vcs(self):
         """
         Get git binary executable path
         """
-        vcs = _execute('which hg', strict=True).strip()
+        vcs = _execute('which hg', strict=True, log_errors=False).strip()
         return vcs
 
     def is_used(self):