Update build instructions for ncurses 6 and tcell

Close #357
Close #738

src/README.md

@@ -61,6 +61,45 @@ make install
 make linux
 ```
 
+### With ncurses 6
+
+The official binaries of fzf are built with ncurses 5 because it's widely
+supported by different platforms. However ncurses 5 is old and has a number of
+limitations.
+
+1. Does not support more than 256 color pairs (See [357][357])
+2. Does not support italics
+3. Does not support 24-bit color
+
+[357]: https://github.com/junegunn/fzf/issues/357
+
+But you can manually build fzf with ncurses 6 to overcome some of these
+limitations. ncurses 6 supports up to 32767 color pairs (1), and supports
+italics (2). To build fzf with ncurses 6, you have to install it first. On
+macOS, you can use Homebrew to install it.
+
+```sh
+brew install homebrew/dupes/ncurses
+LDFLAGS="-L/usr/local/opt/ncurses/lib" make install
+```
+
+### With tcell
+
+[tcell][tcell] is a portable alternative to ncurses and we currently use it to
+build Windows binaries. tcell has many benefits but most importantly, it
+supports 24-bit colors. To build fzf with tcell:
+
+```sh
+TAGS=tcell make install
+```
+
+However, note that tcell has its own issues.
+
+- Poor rendering performance compared to ncurses
+- Does not support bracketed-paste mode
+- Does not support italics unlike ncurses 6
+- Some wide characters are not correctly displayed
+
 Test
 ----
 
@@ -88,6 +127,8 @@ Third-party libraries used
     - Licensed under [MIT](http://mattn.mit-license.org)
 - [mattn/go-isatty](https://github.com/mattn/go-isatty)
     - Licensed under [MIT](http://mattn.mit-license.org)
+- [tcell](https://github.com/gdamore/tcell)
+    - Licensed under [Apache License 2.0](https://github.com/gdamore/tcell/blob/master/LICENSE)
 
 License
 -------
@@ -99,4 +140,4 @@ License
 [gil]:     http://en.wikipedia.org/wiki/Global_Interpreter_Lock
 [ncurses]: https://www.gnu.org/software/ncurses/
 [req]:     http://golang.org/doc/install
-[termbox]: https://github.com/nsf/termbox-go
+[tcell]:   https://github.com/gdamore/tcell