Add Angel Ezquerra to contributors list (#651)

Contributors.md

@@ -3,9 +3,20 @@ Main Arraymancer contributors (sorted alphabetically)
 ### Andrea Ferretti (@andreaferetti)
   - Autograd of mean along an axis
 
+### Angel Ezquerra (@AngelEzquerra)
+  - Add features that were missing from Numpy and Matlab, such as:
+    - Missing math functions and operators (contains, convolve, diff_discrete, median, sinc, roll, flatten, append, moveaxes, unique, etc.)
+    - Add or improve diagonal, triangular and other special matrix functions (toepliz, hankel, vander, etc.)
+  - Improve Complex and bool tensor support as well as mixed real-Complex ops
+  - Add support for combining span slices with negative steps (e.g. `t[_|-1]`)
+  - Add support for doing a masked fill from a tensor
+  - Remove some compilation warnings
+  - Error message and documentation improvements
+  - Miscellaneous fixes
+
 ### Eduardo Bart (@edubart)
   - OpenMP
-  - Several performance optimizations and fix including
+  - Several performance optimizations and fixes including
     - Strided iterators
     - Uninitialized seq
   - Shapeshifting procs