Don't jump a whole line on DEL at the leftmost indentation

The previous behavior was to jump to the previous line by hitting DEL
just once when there were no indentation points to the left anymore.
This was quite confusing and almost never intended from the user's
point of view.  If the user is still backspacing when there are no
indentation points left, chances are that we screwed up something
already and the user is intending to indent somewhere unknown.  Better
to just fallback to regular DEL behavior then.
Add customization option and NEWS entry for the DEL on first indentation change
Merge pull request #189 from errge/master

Don't jump a whole line on DEL at the leftmost indentation
Add convenient navigation keys n/p for `haskell-menu'
Handle non-existant sessions with non-existant processes in `haskell-menu'
Remove spurious keymap from `haskell-menu`
Switch to session's buffer on RET in `haskell-menu`
Major Info manual update

This commit integrates most of the config/setup content from the
`README.md` file into the Info manual and adds some more additional
content.
Major overhaul of `README.md` removing config instructions

As the content has been moved to the Info manual (see 25d61a7) the
information contained in `README.md` is now redundant. Now `README.md`
simply refers to the latest Info manual HTML snapshot (which has been
updated as well via 1753d49939).
Revert "Highlight with 0 or more occurrences."

The original commit has been identified as the cause for Emacs freezing up
during font-locking. This revert closes #190 and fixes #182.

This reverts commit 05a46adc1def7f699e5e83db02e21f42ee799253 (re #160).
Improve top-level declaration font-locking in presence of newlines

This commit is a 2nd attempt at what b458cdf (re #160) tried to
accomplish. To keep it simple, only a single optional newline is
tolerated after the top-level identifier. Moreover, in case Bird-style
syntax is active, this feature is disabled altogether.
Add new `haskell-cabal-find-pkg-desc` defun

This is basically a port of Cabal's `findPackageDesc` function[1] but
without the exception throwing. This function attempts to match
closely Cabal's algorithm for locating the `.cabal` file.

 [1]: http://hackage.haskell.org/packages/archive/Cabal/1.16.0.3/doc/html/Distribution-Simple-Utils.html
Remove obsolete `autoload` statement
Remove obsolete comment and spurious top-level `4` value

The `4` seems to have been added in da1169202 by accident, as it
doesn't seem to serve any useful purpose.
Refactor `haskell-cabal-{compute-checksum,find-file}'

This commit adds proper docstrings and refactors the two functions in
terms of the new `haskell-cabal-find-pkg-desc' function added in
5b02b04. Because by using `haskell-cabal-find-pkg-desc' the
implementation becomes more faithful to the way Cabal locates `.cabal`
files, there are subtle semantic changes caused by this
commit. However, since the goal is to emulate Cabal as close as
possible, this should be alright.
Add optional DIR argument to `haskell-cabal-find-dir'

See also 8bc372d where a DIR argument was added to
`haskell-cabal-find-file' as well.
Add convenience command `haskell-cabal-visit-file'

`haskell-cabal-visit-file` allows for quickly locating and jumping to
the nearest .cabal file from a Haskell source buffer, you can now use
`M-x haskell-cabal-visit-file`; with a prefix argument the .cabal is
visited in the "other window".

This commit also updates NEWS and mentions this command in the Info
manual.

Note: This feature has been kept orthogonal to haskell-session.el, as
  it would only complicate an otherwise simple implementation. Should
  the need arise for a `haskell-session`-aware variant, we can always
  define a second version in `haskell-session.el` tightly integrated
  with the `haskell-session` framework.
Add section about rectangle commands to Info manual
Minor rewordings, typo fixes and @xref-fixes in Info manual

The use of @pxref/@xref/@ref is a bit cumbersome, as the result
differs significantly depending on whether html, info or tex output is
generated.
Remove trailing periods from NEWS items