Drop the PartialEq and Eq impls on Regex.

It is misleading to suggest that Regex implements equality, since
equality is a well defined operation on regular expressions and this
particular implementation doesn't correspond to that definition at all.

Moreover, I suspect the actual use cases for such an impl are rather
niche. A simple newtype+deref should resolve any such use cases.

Fixes #178

src/re_unicode.rs

@@ -136,18 +136,6 @@ impl From<Exec> for Regex {
     }
 }
 
-/// Equality comparison is based on the original string. It is possible that
-/// different regular expressions have the same matching behavior, but are
-/// still compared unequal. For example, `\d+` and `\d\d*` match the same set
-/// of strings, but are not considered equal.
-impl PartialEq for Regex {
-    fn eq(&self, other: &Regex) -> bool {
-        self.as_str() == other.as_str()
-    }
-}
-
-impl Eq for Regex {}
-
 impl FromStr for Regex {
     type Err = Error;
 

tests/api_str.rs

@@ -19,9 +19,3 @@ fn empty_match_unicode_captures_iter() {
                        .collect();
     assert_eq!(vec![(0, 0), (3, 3), (4, 4), (7, 7), (8, 8)], ms);
 }
-
-#[test]
-fn eq() {
-    use regex::Regex;
-    assert_eq!(regex!(r"[a-z]+"), Regex::new("[a-z]+").unwrap());
-}

tests/misc.rs

@@ -8,14 +8,7 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-use regex::Regex;
-
 mat!(prefix_literal_match, r"^abc", r"abc", Some((0, 3)));
 mat!(prefix_literal_nomatch, r"^abc", r"zabc", None);
 mat!(one_literal_edge, r"abc", r"xxxxxab", None);
 matiter!(terminates, r"a$", r"a", (0, 1));
-
-#[test]
-fn eq() {
-    assert_eq!(regex!(r"[a-z]+"), Regex::new("[a-z]+").unwrap());
-}