New command defining format, minor improvements

- If the second address is empty, it is assumed to be `.`
- Regex addresses and `:substitute` now integrate with search history and
  respect case sensitivity settings
- Patterns for `:substitute` can't be delimited by
- `:set` now supports inverting options using `:set inv{option}` and
  `:set {option}!`
- New commands: `:new`, `:vnew`, `:exit`, `:xall`, `:wall`, `:qall`, `:update`

lib/utils.coffee

@@ -0,0 +1,36 @@
+_ = require 'underscore-plus'
+
+module.exports =
+  getSearchTerm: (term, modifiers = {'g': true}) ->
+    escaped = false
+    hasc = false
+    hasC = false
+    term_ = term
+    term = ''
+    for char in term_
+      if char is '\\' and not escaped
+        escaped = true
+        term += char
+      else
+        if char is 'c' and escaped
+          hasc = true
+          term = term[...-1]
+        else if char is 'C' and escaped
+          hasC = true
+          term = term[...-1]
+        else if char isnt '\\'
+          term += char
+        escaped = false
+
+    if hasC
+      modifiers['i'] = false
+    if (not hasC and not term.match('[A-Z]') and \
+        atom.config.get('vim-mode.useSmartcaseForSearch')) or hasc
+      modifiers['i'] = true
+
+    modFlags = Object.keys(modifiers).filter((key) -> modifiers[key]).join('')
+
+    try
+      new RegExp(term, modFlags)
+    catch
+      new RegExp(_.escapeRegExp(term), modFlags)