increase default dev donation

based on the reddit poll we get 45.99% support to increase the developer donation
https://www.reddit.com/r/MoneroMining/comments/6eu00j/question_xmrstak_default_donation_increase_to_2/

README.md

@@ -85,7 +85,7 @@ Performance is nearly identical to the closed source paid miners. Here are some
 * **Dual E5640** - 365 H/s (same as above)
 
 ## Default dev donation
-By default the miner will donate 1% of the hashpower (1 minute in 100 minutes) to my pool. If you want to change that, edit **donate-level.h** before you build the binaries.
+By default the miner will donate 2% of the hashpower (2 minute in 100 minutes) to my pool. If you want to change that, edit **donate-level.h** before you build the binaries.
 
 If you want to donate directly to support further development, here is my wallet
 

donate-level.h

@@ -3,8 +3,8 @@
 /*
  * Dev donation.
  * Percentage of your hashing power that you want to donate to the developer, can be 0.0 if you don't want to do that.
- * Example of how it works for the default setting of 1.0:
- * You miner will mine into your usual pool for 99 minutes, then switch to the developer's pool for 1.0 minute.
+ * Example of how it works for the default setting of 2.0:
+ * You miner will mine into your usual pool for 98 minutes, then switch to the developer's pool for 2.0 minute.
  * Switching is instant, and only happens after a successful connection, so you never loose any hashes.
  *
  * If you plan on changing this setting to 0.0 please consider making a one off donation to my wallet:
@@ -12,4 +12,4 @@
  *
  */
 
-constexpr double fDevDonationLevel = 1.0 / 100.0;
+constexpr double fDevDonationLevel = 2.0 / 100.0;