refactoring test/

pull test cases to `common-testCases.js` and `common-testCases-error.js`
framework tests then includes these files to reduces duplication and make tests more consistent between the frameworks

 On branch test-refactor
 Changes to be committed:
	new file:   test/common-testCases-error.js
	new file:   test/common-testCases.js
	modified:   test/core-handleError.js
	modified:   test/core.js
	modified:   test/express-handleError.js
	modified:   test/express.js
	modified:   test/union-handleError.js
	modified:   test/union.js
[feature] add file size to file listing

Show size of files in listing
Added humanReadable and si options to customize the file size (see `ls`)
Fixed jshint warnings

On branch feature-file-listing
 Changes to be committed:
	modified:   lib/ecstatic.js
	modified:   lib/ecstatic/opts.js
	modified:   lib/ecstatic/showdir.js
[test] Simplify exports and variable names
Human readable file sizes in listings
Opts for human-readable and si
Document humanReadable options
v0.4.13
Print url in cli
Use minimist instead of optimist
Fix humanReadable docs
Turn on listings by default
Fallback to UTF-8 encoding in case when mime.charsets.lookup returns undefined.

Summary: This solves issue when javascript files are not served with UTF-8 because their content type is application/json and mime.charsets.lookup return UTF-8 only for files that match /^text\// regex
Add contributing guidelines