Fix: blank line added by HgRepo.ReadCommandOutput().

The extra blank line showed up as a change when running :Hgvdiff
Merge pull request #1 from shaneharper/fix_blank_line_appended_to_hg_output

Fix: remove blank line added by HgRepo.ReadCommandOutput().
Fix `Hgstatus` incorrectly saying nothing has changed.
Add variants of existing commands that open things in a new tab page.
Correctly escape paths on Windows.
More path escaping!
Check before cleaning any empty buffers left after new tab commands.
New command to export a patch and allow existing log command to take options.

* Hglogexport command takes patch name as input. If the env variable
  HG_EXPORT_PATCH_DIR is set, then the patch will be created under it.
  Otherwise, it will be created in the directory from which vim
  was launched.

* HgLog command takes options that can be passed to hg log command.
  E.g., the following command will list just 3 logs by user bob.
  :Hglog -u bob -l 3

Testing:
* Patch gets created under the right directory when env variable is set
  and not set.

* Hglog command honors -u and -l options. It also works when current
  file name is given as input --> :Hglog % -u bob -l 3
`Hglogexport` uses relative paths correctly on Windows, auto-completes to files.
Another attempt to fix weird issues with cleaning up diff buffers.
Make sure paths in the commit message are relative to the repo.

--HG--
extra : rebase_source : 92e0f8b56491dc64572053322f0a684e308bc972
`Hgannotate` improvements.
* `Hgwannotate` opens a wide/verbose version of annotations.
* Both commands can take a filename to open first.
Fix typo bug, annotate window width.

--HG--
extra : amend_source : c9869383eff0ee449114b4928dd71c0182910980
Syntax highlighting for `Hgwannotate`.
Handle absolute/relative paths properly.
Fix for Lawrencium files having folded sections deleted incorrectly.
Keep alternate buffer intact when opening the status window.
More advanced way to know what window to pick to show a diff summary.
Ignore tags
Fix stupid typo, make sure paths are normalized.