Remove unused dependencies

This is a backport of #117 for the 2.x branch

package.json

@@ -26,8 +26,6 @@
   },
   "homepage": "https://github.com/MetaMask/eth-sig-util#readme",
   "dependencies": {
-    "buffer": "^5.2.1",
-    "elliptic": "^6.4.0",
     "ethereumjs-abi": "0.6.5",
     "ethereumjs-util": "^5.1.1",
     "tweetnacl": "^1.0.0",

yarn.lock

@@ -101,11 +101,6 @@ balanced-match@^1.0.0:
   resolved "https://registry.yarnpkg.com/balanced-match/-/balanced-match-1.0.0.tgz#89b4d199ab2bee49de164ea02b89ce462d71b767"
   integrity sha1-ibTRmasr7kneFk6gK4nORi1xt2c=
 
-base64-js@^1.0.2:
-  version "1.3.0"
-  resolved "https://registry.yarnpkg.com/base64-js/-/base64-js-1.3.0.tgz#cab1e6118f051095e58b5281aea8c1cd22bfc0e3"
-  integrity sha512-ccav/yGvoa80BQDljCxsmmQ3Xvx60/UpBIij5QN21W3wBi/hhIC9OoO+KLpu9IJTS9j4DRVJ3aDDF9cMSoa2lw==
-
 bindings@^1.2.1:
   version "1.3.0"
   resolved "https://registry.yarnpkg.com/bindings/-/bindings-1.3.0.tgz#b346f6ecf6a95f5a815c5839fc7cdb22502f1ed7"
@@ -160,14 +155,6 @@ buffer-xor@^1.0.3:
   resolved "https://registry.yarnpkg.com/buffer-xor/-/buffer-xor-1.0.3.tgz#26e61ed1422fb70dd42e6e36729ed51d855fe8d9"
   integrity sha1-JuYe0UIvtw3ULm42cp7VHYVf6Nk=
 
-buffer@^5.2.1:
-  version "5.2.1"
-  resolved "https://registry.yarnpkg.com/buffer/-/buffer-5.2.1.tgz#dd57fa0f109ac59c602479044dca7b8b3d0b71d6"
-  integrity sha512-c+Ko0loDaFfuPWiL02ls9Xd3GO3cPVmUobQ6t3rXNUk304u6hGq+8N/kFi+QEIKhzK3uwolVhLzszmfLmMLnqg==
-  dependencies:
-    base64-js "^1.0.2"
-    ieee754 "^1.1.4"
-
 callsites@^3.0.0:
   version "3.1.0"
   resolved "https://registry.yarnpkg.com/callsites/-/callsites-3.1.0.tgz#b3630abd8943432f54b3f0519238e33cd7df2f73"
@@ -331,7 +318,7 @@ drbg.js@^1.0.1:
     create-hash "^1.1.2"
     create-hmac "^1.1.4"
 
-elliptic@^6.2.3, elliptic@^6.4.0:
+elliptic@^6.2.3:
   version "6.4.0"
   resolved "https://registry.yarnpkg.com/elliptic/-/elliptic-6.4.0.tgz#cac9af8762c85836187003c8dfe193e5e2eae5df"
   integrity sha1-ysmvh2LIWDYYcAPI3+GT5eLq5d8=
@@ -778,11 +765,6 @@ iconv-lite@^0.4.24:
   dependencies:
     safer-buffer ">= 2.1.2 < 3"
 
-ieee754@^1.1.4:
-  version "1.1.12"
-  resolved "https://registry.yarnpkg.com/ieee754/-/ieee754-1.1.12.tgz#50bf24e5b9c8bb98af4964c941cdb0918da7b60b"
-  integrity sha512-GguP+DRY+pJ3soyIiGPTvdiVXjZ+DbXOxGpXn3eMvNW4x4irjqXm4wHKscC+TfxSJ0yw/S1F24tqdMNsMZTiLA==
-
 ignore@^4.0.6:
   version "4.0.6"
   resolved "https://registry.yarnpkg.com/ignore/-/ignore-4.0.6.tgz#750e3db5862087b4737ebac8207ffd1ef27b25fc"