update(commit_levels): fix minor typos, links, and duplication

also fix issues identified by @topherfangio

docs/guides/COMMIT_LEVELS.md

@@ -4,7 +4,7 @@ The Angular Material team has a very specific process for change commits.
 
 Our commit process is intentionally restrictive to (a) support the rapid evolution of Angular Material and (b) manage change complexity and coding standards within the framework. 
 
-Angular Material uses a "Pull Request" process to allow team leaders opportunities to maintain code reviews, ensure sanity checks, encourage coding standards, and provide feedbackto the developer. 
+Angular Material uses a "Pull Request" process to allow team leaders opportunities to maintain code reviews, ensure sanity checks, encourage coding standards, and provide feedback to the developer. 
 
 #### General Rules
 
@@ -25,7 +25,7 @@ Angular Material uses a "Pull Request" process to allow team leaders opportuniti
 
 The development team has defined three (3) Github levels of **commit authorization** within [Angular/Material](https://github.com/angular/material/):
 
-* General : 
+* General: 
   * Developers in this group includes any team members not listed under Core or Team Leads below
   * For any and all changes, developers must use a fork of the Angular Material repository 
     * Please do not make or submit any changes from the master branch. 
@@ -35,14 +35,14 @@ The development team has defined three (3) Github levels of **commit authorizati
   * Should ensure their issues are tested with latest HEAD versions of Angular Material
   * Should ensure their issues are tested with latest releases of Angular (1.3.x, 1.4.x, 1.5.x)
 * Core: 
-  * Includes: [Ryan Schmukler](@rschmukler), [Robert Messerlee](@robertmesserle), [Topher Fangio](@topherfangio)
+  * Includes: [Ryan Schmukler](https://github.com/rschmukler), [Robert Messerlee](https://github.com/robertmesserle), [Topher Fangio](https://github.com/topherfangio)
   * Should not merge PRs (unless explicitly requested)
   * Should use Angular Material branches for major, non-trivial changes. 
-  * For minor changes, developers in this groupmay elect to commit direct to master for minor changes.
+  * For minor changes, developers in this group may elect to commit direct to master.
 * Team Leads:
-  * Includes: [Naomi Black](@naomiblack), [Thomas Burleson](@thomasburleson), [Jeremy Elbourn](@jelbourn)
+  * Includes: [Naomi Black](https://github.com/naomiblack), [Thomas Burleson](https://github.com/ThomasBurleson), [Jeremy Elbourn](https://github.com/jelbourn)
   * May review PRs
     * ThomasBurleson is the primary PR reviewer 
-    * Should perform confirm Karma test pass
+    * Should confirm Karma tests pass
     * Should squash as need
     * Should ensure the PR is closed when the merge finishes.