Remove unnecessary encoding comments

Because default script encoding is Encoding::UTF-8 after v2.0 and our
requirements is Ruby >= 2.1.0.
http://www.ruby-doc.org/core-2.1.1/Encoding.html#class-Encoding-label-Script+encoding
Remove redundant if statement
Fix bug appending path name of last board to `selected`
simplify prev_menu operation
Merge pull request #7 from yous/patch-develop

Progress
Merge pull request #8 from synthdnb/develop

simplify prev_menu operation
now user can actually "select" board!
remove unneccessary require
add skeleton for terminal header and footer
print current_board in header
add FIXMEs to not implemented feature
implements (B)oard in main menu
add Post model
Add SOURCE_ANNOTATION_DIRECTORIES environment variable for `rake notes`

http://guides.rubyonrails.org/command_line.html#notes

Close #10
fix rubocop errors
Merge pull request #11 from yous/patch-notes

Add SOURCE_ANNOTATION_DIRECTORIES environment variable for `rake notes`