Document workarounds for lower Vim versions

see also #23

README.md

@@ -45,7 +45,8 @@ Unicode symbols (e.g. `α`). By default, these substitutions must be triggered e
 `<Tab>` key, as in the Julia command line (the REPL); however, an automatic, as-you-type mode can also
 be activated.
 
-These features are only available with Vim version 7.4 or higher.
+These features only work as described with Vim version 7.4 or higher. Tab completion can still be made
+available on lower Vim versions, see below for more details.
 
 The following sections provide details on this features. The complete documentation is provided by calling
 `:help julia-vim` from within Vim.
@@ -88,6 +89,20 @@ substitution to Unicode.
 [YouCompleteMe]: https://github.com/Valloric/YouCompleteMe
 [neocomplcache]: https://github.com/Shougo/neocomplcache.vim
 
+#### Using this feature on Vim versions lower than 7.4
+
+The automatic remapping of the `<Tab>` key is not performed if Vim version is lower than 7.4. However, the
+functionality can still be used via the omnicompletion mechanism, i.e. by using `CTRL-X + CTRL-O`. You can
+map this to some more convenient key combination, e.g. you may want to add something like this line to your
+`.vimrc` file:
+
+```
+inoremap <C-Tab> <C-X><C-O>
+```
+
+This would map the functionality to `CTRL-Tab`. However, if you try to map this to `<Tab>`, you'd only be
+able to use literal `<Tab>` by using `CTRL-V + <Tab>`.
+
 ### LaTeX-to-Unicode as you type
 
 An automatic substitution mode can be activated by using the command `:let g:julia_auto_latex_to_unicode = 1`,
@@ -104,3 +119,5 @@ This does not interfere with the `<Tab>` mapping discussed above.
 
 The `g:julia_auto_latex_to_unicode` setting can also be changed from the Vim command-line, but you will
 also need to give the command `:call JuliaLaTeXtoUnicodeInit()` for the change to take effect.
+
+This feature is not available with Vim versions lower then 7.4.

doc/julia-vim.txt

@@ -58,7 +58,9 @@ This Vim plug-in extends this functionality:
   - optionally, symbols are substituted on the fly as you type them, see
     |julia-vim-L2U-as-you-type|
 
-These features are only available with Vim version 7.4 or higher.
+These features only work as described with Vim version 7.4 or higher. Tab
+completion can still be made available on lower Vim versions, see
+|julia-vim-L2U-workaround|.
 
 ------------------------------------------------------------------------------
 LATEX TO UNICODE VIA TAB KEY                    *julia-vim-L2U-tab*
@@ -116,14 +118,29 @@ match for `\nequiv` (`≢`). By default, if <Tab> finds an exact match performs
 the substitution, but this can be controlled by the
 |g:julia_latex_to_unicode_eager| setting.
 
+Vim versions lower than 7.4                     *julia-vim-L2U-workaround*
+
+The <Tab> key remapping is not performed by default with Vim versions lower
+than 7.4. However, the functionality is still available via onmicompletion,
+which is accessible by the CTRL-X CTRL-O key combination. You can map some
+other key combination to this by adding something like
+>
+  inoremap <C-Tab> <C-X><C-O>
+<
+in your |.vimrc| file. If you'd map <Tab> directly, then you'd need to use
+CTRL-V <Tab> to insert a literal <Tab>.
+
+The settings |g:julia_latex_to_unicode_eager| and
+|g:julia_latex_suggestions_enabled| are still meaningful in this case.
 
 ------------------------------------------------------------------------------
 LATEX TO UNICODE AS YOU TYPE                    *julia-vim-L2U-as-you-type*
 
-This feature is disabled by default, see |g:julia_auto_latex_to_unicode|. It
-consists in substituting valid LaTeX sequences with Unicode symbols
-automatically as the typing progresses, as soon as the sequences is
-unambiguously complete. For example, when typing:
+This feature is disabled by default, see |g:julia_auto_latex_to_unicode|, and
+it is only available with Vim version 7.4 or higher. It consists in
+substituting valid LaTeX sequences with Unicode symbols automatically as the
+typing progresses, as soon as the sequences is unambiguously complete. For
+example, when typing:
 >
     \chi\^2 = 1
 <