Added minlength to the validTagAttributes array on multiple elements

[rolandoisidoro]

This PR refers to issue #206. It will allow developers to set minlength attribute on text, email, search, password, tel and url form elements, which will enable HTML5 minimum length validation.

[froschdesign]

@rolandoisidoro
Please extend also the unit tests. Example:

zend-form/test/View/Helper/FormTextTest.php

Lines 48 to 81 in 4419eef

	public function validAttributes()
	{
	return [
	['name', 'assertContains'],
	['accept', 'assertNotContains'],
	['alt', 'assertNotContains'],
	['autocomplete', 'assertContains'],
	['autofocus', 'assertContains'],
	['checked', 'assertNotContains'],
	['dirname', 'assertContains'],
	['disabled', 'assertContains'],
	['form', 'assertContains'],
	['formaction', 'assertNotContains'],
	['formenctype', 'assertNotContains'],
	['formmethod', 'assertNotContains'],
	['formnovalidate', 'assertNotContains'],
	['formtarget', 'assertNotContains'],
	['height', 'assertNotContains'],
	['list', 'assertContains'],
	['max', 'assertNotContains'],
	['maxlength', 'assertContains'],
	['min', 'assertNotContains'],
	['multiple', 'assertNotContains'],
	['pattern', 'assertContains'],
	['placeholder', 'assertContains'],
	['readonly', 'assertContains'],
	['required', 'assertContains'],
	['size', 'assertContains'],
	['src', 'assertNotContains'],
	['step', 'assertNotContains'],
	['value', 'assertContains'],
	['width', 'assertNotContains'],
	];
	}

[rolandoisidoro]

@froschdesign , just extended the tests you mentioned before and added missing tests for FormSearchViewHelper.

[weierophinney]

Thanks, @rolandoisidoro!