add iterm2 shell integration

.iterm2/it2check

@@ -0,0 +1,88 @@
+#!/bin/bash
+# Make sure stdin and stdout are a tty.
+if [ ! -t 0 ] ; then
+  exit 1
+fi
+if [ ! -t 1 ] ; then
+  exit 1
+fi
+
+# Save the tty's state.
+saved_stty=$(stty -g)
+
+# Trap ^C to fix the tty.
+trap ctrl_c INT
+
+function ctrl_c() {
+  stty "$saved_stty"
+  exit 1
+}
+
+# Read some bytes from stdin. Pass the number of bytes to read as the first argument.
+function read_bytes()
+{
+  numbytes=$1
+  dd bs=1 count=$numbytes 2>/dev/null
+}
+
+function read_dsr() {
+  # Reading response to DSR.
+  dsr=""
+  spam=$(read_bytes 2)
+  byte=$(read_bytes 1)
+  while [ "${byte}" != "n" ]; do
+    dsr=${dsr}${byte}
+    byte=$(read_bytes 1)
+  done
+  echo ${dsr}
+}
+
+# Extract the terminal name from DSR 1337
+function terminal {
+  echo -n "$1" | sed -e 's/ .*//'
+}
+
+# Extract the version number from DSR 1337
+function version {
+  echo -n "$1" | sed -e 's/.* //'
+}
+
+# Enter raw mode and turn off echo so the terminal and I can chat quietly.
+stty -echo -icanon raw
+
+# Support for the extension first appears in this version of iTerm2:
+MIN_VERSION=2.9.20160304
+if [ $# -eq 1 ]; then
+  MIN_VERSION=$1
+fi
+
+# Send iTerm2-proprietary code. Other terminals ought to ignore it (but are
+# free to use it respectfully).  The response won't start with a 0 so we can
+# distinguish it from the response to DSR 5. It should contain the terminal's
+# name followed by a space followed by its version number and be terminated
+# with an n.
+echo -n ''
+
+# Report device status. Responds with esc [ 0 n. All terminals support this. We
+# do this because if the terminal will not respond to iTerm2's custom escape
+# sequence, we can still read from stdin without blocking indefinitely.
+echo -n ''
+
+version_string=$(read_dsr)
+if [ "${version_string}" != "0" -a "${version_string}" != "3" ]; then
+  # Already read DSR 1337. Read DSR 5 and throw it away.
+  dsr=$(read_dsr)
+else
+  # Terminal didn't respond to the DSR 1337. The response we read is from DSR 5.
+  version_string=""
+fi
+
+# Restore the terminal to cooked mode.
+stty "$saved_stty"
+
+# Extract the terminal name and version number from the response.
+version=$(version "${version_string}")
+term=$(terminal "${version_string}")
+
+# Check if they match what we're looking for. This becomes the return code of the script.
+test "$term" = ITERM2 -a \( "$version" \> "$MIN_VERSION" -o "$version" = "$MIN_VERSION" \)