Added Huffman encoding program

Described here: http://rosettacode.org/wiki/Huffman_coding
Added Huffman encoding program

Described here: http://rosettacode.org/wiki/Huffman_coding
Merge branch 'huffman-coding' of github.com:yuanchenyang/rust-rosetta into huffman-coding

Conflicts:
	src/huffman_encoding.rs
Cleaned up files and added README item
Function names use underscores, simplify Ord and Eq implementations
Merge pull request #119 from yuanchenyang/huffman-coding

Huffman coding
string_matching: Stylistic updates.
perfect_numbers: Stylistic updates.
dot_product: Stylistic updates.
n_queens: Stylistic updates.
Knapsack

Fixed name merge

rewrote display functionality into main

removed unused deriving

removed unused deriving Show

actually remove deriving show

Removed whitespace on empty line
Merge pull request #123 from JakeMick/knapsack

Knapsack
change not_tested attribute to a magic comment
colorize warning for 100 columns
fix formatting and spacing
fix rand imports from extern to std
Merge pull request #125 from jschaf/tweak-build

colorize warning for 100 columns
Merge pull request #126 from jschaf/fix-imports

Fix rand imports and some long lines
Fix build errors
Fix merge conflicts