Merge branch 'master' into staging_065

Conflicts were:
- README.md: Two commits targeted the brightness table. #781 from
14. April 2018 on master and #684 from 05. December 2017 on next.
- powerlevel9k.zsh-theme: Two commits targeted the rbenv segment. Both
achieve the same thing: To show the Ruby version number always. #795 on
next from 14. April 2018 and #610 on master from 28. September 2017. I
went with #795 here as this - although being newer - is the one on
master, and that should be more stable.

test/segments/dir.spec

@@ -46,6 +46,27 @@ function testTruncateFoldersWorks() {
   unset POWERLEVEL9K_SHORTEN_STRATEGY
 }
 
+function testTruncateFolderWithHomeDirWorks() {
+  POWERLEVEL9K_SHORTEN_DIR_LENGTH=1
+  CURRENT_DIR=$(pwd)
+
+  cd ~
+  FOLDER="powerlevel9k-test-${RANDOM}"
+  mkdir -p $FOLDER
+  cd $FOLDER
+  # Switch back to home folder as this causes the problem.
+  cd ..
+
+  assertEquals "%K{blue} %F{black}~ %k%F{blue}%f " "$(build_left_prompt)"
+
+  rmdir $FOLDER
+  cd ${CURRENT_DIR}
+
+  unset CURRENT_DIR
+  unset FOLDER
+  unset POWERLEVEL9K_SHORTEN_DIR_LENGTH
+}
+
 function testTruncateMiddleWorks() {
   POWERLEVEL9K_SHORTEN_DIR_LENGTH=2
   POWERLEVEL9K_SHORTEN_STRATEGY='truncate_middle'