Update README.rst with info about bad components (#256)

* Update README.rst

Add note that some cheap boards from chinese manufactures my be using the components that do not meet with required parameters.

README.rst

@@ -211,7 +211,7 @@ Troubleshooting
   #. Animal RFID tags are not supported. They use a different frequency (125 kHz).
   #. Hardware may be corrupted, most products are from china and sometimes the quality is really poor. Contact your seller.
   #. Newer versions of Mifare cards like DESFire/Ultralight maybe not work according to missing authentification, see `security`_ or different `protocol`_.
-
+  #. Some boards bought from chinese manufactures do not use the best components and this can affect the detection of different types of tag/card. In some of these boards, the L1 and L2 inductors do not have a high enough current so the signal generated is not enough to get Ultralight C and NTAG203 tags to work, replacing those with same inductance (2.2uH) but higher operating current inductors should make things work smoothly. Also, in some of those boards the  harmonic and matching circuit needs to be tuned, for this replace C4 and C5 with 33pf capacitors and you are all set. (Source: `Mikro Elektronika`_) 
 
 * **My mobile phone doesn't recognize the MFRC522** or **my MFRC522 can't read data from other MFRC522**
 
@@ -277,3 +277,4 @@ It has been extended with functionality to alter sector 0 on Chinese UID changea
 .. _supported by hardware: https://web.archive.org/web/20151210045625/http://www.nxp.com/documents/leaflet/939775017564.pdf
 .. _Arduino forum: https://forum.arduino.cc
 .. _stdint.h: https://en.wikibooks.org/wiki/C_Programming/C_Reference/stdint.h
+.. _Mikro Elektronika: https://forum.mikroe.com/viewtopic.php?f=147&t=64203