Added ShellSession language using pygments Bash Session lexer

samples/ShellSession/dollar.sh-session

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+$ echo $FOOBAR
+Hello World!

samples/ShellSession/gem-install.sh-session

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+$ gem install nokogiri
+...
+Building native extensions. This could take a while...
+...
+checking for libxml/parser.h... *** extconf.rb failed ***
+Could not create Makefile due to some reason, probably lack of
+necessary libraries and/or headers. Check the mkmf.log file for more
+details. You may need configuration options.
+...
+ 
+$ brew tap homebrew/dupes
+Cloning into '/usr/local/Library/Taps/homebrew-dupes'...
+remote: Counting objects: 1034, done.
+remote: Compressing objects: 100% (591/591), done.
+remote: Total 1034 (delta 560), reused 898 (delta 443)
+Receiving objects: 100% (1034/1034), 192.53 KiB | 0 bytes/s, done.
+Resolving deltas: 100% (560/560), done.
+Checking connectivity... done
+Warning: Could not tap homebrew/dupes/lsof over mxcl/master/lsof
+Tapped 41 formula
+ 
+$ brew install apple-gcc42
+==> Downloading http://r.research.att.com/tools/gcc-42-5666.3-darwin11.pkg
+######################################################################## 100.0%
+==> Caveats
+NOTE:
+This formula provides components that were removed from XCode in the 4.2
+release. There is no reason to install this formula if you are using a
+version of XCode prior to 4.2.
+ 
+This formula contains compilers built from Apple's GCC sources, build
+5666.3, available from:
+ 
+http://opensource.apple.com/tarballs/gcc
+ 
+All compilers have a `-4.2` suffix. A GFortran compiler is also included.
+==> Summary
+🍺 /usr/local/Cellar/apple-gcc42/4.2.1-5666.3: 104 files, 75M, built in 11 seconds
+ 
+$ gem install nokogiri -v 1.5.10
+Fetching: nokogiri-1.5.10.gem (100%)
+Building native extensions. This could take a while...
+Successfully installed nokogiri-1.5.10
+1 gem installed
+Installing ri documentation for nokogiri-1.5.10...
+Installing RDoc documentation for nokogiri-1.5.10...
+

samples/ShellSession/simple.sh-session

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+> echo $FOOBAR
+Hello World!