Conditional calling of pathogen#infect

Plus changing of the default font
More gitignore globs
Specify DiffText highlighting
Improved zshrc

- improved structure: for non-interactive shells just quit early instead
  of going through the whole file to find out the end of "if" statement
- make use of expansion in prompt (prompt_subst)
- make use of vcs_info in prompt
- make use of %F %f prompt expansion escapes instead of manual codes