view: clean up utf8_width() API
configure: only pass bug email to AC_INIT

This makes `./configure --help` print:

    Report bugs to <jonas.fonseca@gmail.com>.
Skip confirmation step when editor reports no error

Instead of prompting the user to 'Press Enter to continue', drop
directly back into last view after edit when no error was reported by
the editor

References #200
Fix calculation of line number for first line in file

Commit 8c132e2a5b520754a432068dc8b1b3fcc3ab899e revealed a bug where the
editor would be opened on the second line of the file instead of the
first one due to wrong calculation of the line number.
Refactor loading of views that are not associated with any view state

This fixes a regression in the loading of the stash view and will
ideally reduce this kind of regressions in the future.
help: support refreshing to show new bindings added via the prompt
prompt: fix cursor position for prompts longer than one character

This can be reproduced by opening the grep view from within Tig while
the main view is loading in the background. The prompt position was
assuming that the prompt has a size of one.
blame: parse author email to support author toggling
Use email instead of name as the key in the author ident cache

This ensures that toggling will work correctling when there are two
authors with the same name.
Check return value from signal()

Error out if signal handler setup fails.

Fixes #246
options: reuse color name parser for obsolete color mappings
tree: add directory color type for use by draw_filename

This fixes coloring of directory names in the tree view by introducing a
new 'directory' color type used instead of 'tree-dir'. It also renames
existing 'filename' color to 'file' to make color names a bit more
consistent wrt. 'file-size'.
tree: use directory and file line types
refs: rename refs module to refdb
refs: rename branch view to refs view

Change the name of the branch view (as discussed in #257) in preparation
for enhancing the branch view to also show tags (issue #134).
refs: use refs_ prefix for internal methods and variables
repo: workaround empty --show-prefix output from certain git versions
argv: separate git log parameters from diff parameters

Parse of git log parameters and ensure they end up in %(revargs) rather
than %(cmdlineargs). This fixes use cases where tig is opened with some
search (e.g. `tig -SREQ_SCROLL_PAGE_UP`) and the diff view is opened
either from the main view or for example via the blame view.
options: enable graph when --graph is passed
main: use --pretty=raw format if reflog output is requested

This fixes a regression where `tig -g` would no longer show the proper
reflog messages.