Added Mechmini 2.0 to Mechmini keyboard folder

This creates a v1 and v2 subproject.  V1 retains all the same implementations of the bootmapper-ported Mechmnini 1 including #2196.  V2 adds the Mechmini 2.0 kayboard support (I know it took me way to long to get it a pull request in).

All readme's updated to reflect compiling the two seperate keyboards.  Simply either `make mechmini/v1:default` or `make mechmini/v2:defualt`.  Utilizing the rules.mk using `make mechmini:default` will automatically create the Mechmini 2 default keymap as this is the current version and has a much wider user base.

keyboards/mechmini/v1/i2c.h

@@ -0,0 +1,22 @@
+/*
+Copyright 2016 Luiz Ribeiro <luizribeiro@gmail.com>
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 2 of the License, or
+(at your option) any later version.
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+You should have received a copy of the GNU General Public License
+along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+#ifndef __I2C_H__
+#define __I2C_H__
+
+void i2c_init(void);
+void i2c_set_bitrate(uint16_t bitrate_khz);
+uint8_t i2c_send(uint8_t address, uint8_t *data, uint16_t length);
+
+#endif