Add rails compiler plugin

This will be useful for the upcoming unification of the rails and rake
commands.

Author: tpope

compiler/rails.vim

@@ -0,0 +1,37 @@
+" Vim compiler file
+
+if exists("current_compiler")
+  finish
+endif
+
+CompilerSet errorformat=%D(in\ %f),
+      \%\\s%#from\ %f:%l:%m,
+      \%\\s%#from\ %f:%l:,
+      \%\\s%##\ %f:%l:%m,
+      \%\\s%##\ %f:%l,
+      \%\\s%#[%f:%l:\ %#%m,
+      \%\\s%#%f:%l:\ %#%m,
+      \%\\s%#%f:%l:,
+      \%m\ [%f:%l]:,
+      \%+Erake\ aborted!,
+      \%+EDon't\ know\ how\ to\ build\ task\ %.%#,
+      \%+Einvalid\ option:%.%#,
+      \%+Irake\ %\\S%\\+%\\s%\\+#\ %.%#
+
+runtime! compiler/rake.vim
+
+let current_compiler = "rails"
+
+CompilerSet makeprg=rails
+
+CompilerSet errorformat^=
+      \%\\S%\\+\ \ %#%[cefi]%[rxod]%[eir]%[a-z]%#%\\x1b[0m\ %\\+%\\S%\\+%$
+      \%\\&%\\x1b%\\S%\\+\ \ %#%m%\\>%\\x1b[0m\ \ %#%f,
+      \%\\s\ %#%[cefi]%[rxod]%[eir]%[a-z]%#\ %\\+%\\S%\\+%$
+      \%\\&%\\s\ %#%m%\\>\ \ %#%f,
+      \Overwrite%.%#%\\S%\\+\ \ %#%m%\\x1b[0m\ \ %#%f,
+      \%-GOverwrite%.%#\"h\"%.%#,
+      \%+EUsage:\ rails\ %.%#,
+      \%+EType\ 'rails'\ for\ help.
+
+" -complete=customlist,rails#complete_rails