Change initialization to make session work.

Fixes #216.

autoload/UltiSnips.vim

@@ -5,6 +5,7 @@
 if exists('did_UltiSnips_autoload') || &cp || version < 700
     finish
 endif
+let did_UltiSnips_autoload=1
 
 " Define dummy version of function called by autocommand setup in
 " ftdetect/UltiSnips.vim. If the function isn't defined (probably due to
@@ -13,26 +14,10 @@ endif
 function! UltiSnips#FileTypeChanged()
 endfunction
 
-if !exists("g:UltiSnipsUsePythonVersion")
-    let g:_uspy=":py3 "
-    if !has("python3")
-        if !has("python")
-            if !exists("g:UltiSnipsNoPythonWarning")
-                echo  "UltiSnips requires py >= 2.6 or any py3"
-            endif
-            finish
-        endif
-        let g:_uspy=":py "
-    endif
-    let g:UltiSnipsUsePythonVersion = "<tab>"
-else
-    if g:UltiSnipsUsePythonVersion == 2
-        let g:_uspy=":py "
-    else
-        let g:_uspy=":py3 "
-    endif
-endif
-
+call UltiSnips#bootstrap#Bootstrap()
+if !exists("g:_uspy")
+   finish
+end
 
 " FUNCTIONS {{{
 function! s:compensate_for_pum()
@@ -176,13 +161,3 @@ function! UltiSnips#LeavingInsertMode()
     exec g:_uspy "UltiSnips_Manager._leaving_insert_mode()"
 endfunction
 " }}}
-
-" Expand our path
-exec g:_uspy "import vim, os, sys"
-exec g:_uspy "new_path = os.path.abspath(os.path.join(
-    \ vim.eval('expand(\"<sfile>:h\")'), '..', 'pythonx'))"
-exec g:_uspy "vim.command(\"let g:UltiSnipsPythonPath = '%s'\" % new_path)"
-exec g:_uspy "if not hasattr(vim, 'VIM_SPECIAL_PATH'): sys.path.append(new_path)"
-exec g:_uspy "from UltiSnips import UltiSnips_Manager"
-
-let did_UltiSnips_autoload=1

autoload/UltiSnips/bootstrap.vim

@@ -1,5 +1,40 @@
-" Kludge to make sure that this file is really run.
-function! UltiSnips#variables#WasRun()
+let s:SourcedFile=expand("<sfile>")
+
+function! UltiSnips#bootstrap#Bootstrap()
+   if exists('did_UltiSnips_bootstrap')
+      return
+   endif
+   let did_UltiSnips_bootstrap=1
+
+   if !exists("g:UltiSnipsUsePythonVersion")
+       let g:_uspy=":py3 "
+       if !has("python3")
+           if !has("python")
+               if !exists("g:UltiSnipsNoPythonWarning")
+                   echo  "UltiSnips requires py >= 2.6 or any py3"
+               endif
+               finish
+           endif
+           let g:_uspy=":py "
+       endif
+       let g:UltiSnipsUsePythonVersion = "<tab>"
+   else
+       if g:UltiSnipsUsePythonVersion == 2
+           let g:_uspy=":py "
+       else
+           let g:_uspy=":py3 "
+       endif
+   endif
+
+   " Expand our path
+   exec g:_uspy "import vim, os, sys"
+   exec g:_uspy "sourced_file = vim.eval('s:SourcedFile')"
+   exec g:_uspy "while not os.path.exists(os.path.join(sourced_file, 'pythonx')):
+      \ sourced_file = os.path.dirname(sourced_file)"
+   exec g:_uspy "module_path = os.path.join(sourced_file, 'pythonx')"
+   exec g:_uspy "vim.command(\"let g:UltiSnipsPythonPath = '%s'\" % module_path)"
+   exec g:_uspy "if not hasattr(vim, 'VIM_SPECIAL_PATH'): sys.path.append(module_path)"
+   exec g:_uspy "from UltiSnips import UltiSnips_Manager"
 endfunction
 
 " The trigger used to expand a snippet.

autoload/UltiSnips/map_keys.vim

@@ -1,4 +1,4 @@
-call UltiSnips#variables#WasRun()
+call UltiSnips#bootstrap#Bootstrap()
 
 function! UltiSnips#map_keys#MapKeys()
     " Map the keys correctly